Golf ball incorporating an innermost hollow portion

ABSTRACT

Golf ball incorporating a hollow innermost portion that is spherical or aspherical, and a shell layer that is at least partially non-continuous, having a plurality of hollow spaces therein that extend from the inner surface to an outer surface of the shell layer and are symmetrically spaced within the shell layer, wherein the non-continuous shell layer has a first hardness gradient from shell layer inner surface to outer surface of up to about 7 Shore C. An outer core layer has a second hardness gradient and is formed about the outer surface and within the plurality of hollow spaces. The outer core layer has a second inner surface having a second inner surface hardness that differs from the inner surface hardness. Thus, the second inner surface hardness and inner surface hardness may alternate symmetrically and circumferentially about the innermost hollow portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 14/959,190, filed on Dec. 4, 2015, and also acontinuation-in-part of U.S. patent application Ser. Nos. 13/736,993,13/736,997, 13/737,026, and 13/737,041, each filed on Jan. 9, 2013, theentire disclosures of which are hereby incorporated herein by referencein their entireties.

FIELD OF THE INVENTION

This invention relates generally to hollow core golf ball constructionsthat target desirable aerodynamic and/or inertial properties and feelwithout sacrificing durability.

BACKGROUND OF THE INVENTION

In recent years, virtually all golf balls are of a solid construction,typically including a solid core encased by a cover, both of which canhave multiple layers, such as a dual core having a solid center and anouter core layer, or a multi-layer cover having an inner and outer coverlayer. Golf ball cores are often formed at least in part from athermoset rubber composition with polybutadiene as the base rubber. Thecores are usually heated and crosslinked to create a core having certainpre-determined characteristics, such as compression or hardness, whichresult in a golf ball having the properties for a particular group ofplayers, whether it be professionals, low-handicap players, ormid-to-high handicap golfers. From the perspective of a golf ballmanufacturer, it is desirable to have cores exhibiting a wide range ofproperties, such as resilience, durability, spin, and “feel,” becausethis enables the manufacturer to make and sell golf balls suited todiffering levels of ability.

Accordingly, golf ball manufacturers continuously experiment with golfball constructions and material formulations in order to target andimprove aerodynamic and/or inertial properties and achieve desired feelwithout sacrificing durability. One such novel construction with no pastcommercial success is a golf ball having a hollow core—meaning theinnermost portion of the core is hollow, surrounded by a ‘shell layer’and one or more core and cover layers. In some hollow core golf ballconstructions, an aspherical hollow space has been created using aninsert containing hollow spaces.

However, while many prior commercially available golf balls have beenconstructed with non-solid centers such as liquid centers, very few golfballs having hollow centers have ever been pursued. One reason is thatit has been difficult to implement hollow cores in golf ballconstructions and target/improve aerodynamic and/or inertial propertiesand achieve desired feel without sacrificing durability.

Related co-owned U.S. application Ser. No. 14/959,190, filed on Dec. 4,2015 (“'190 application) addresses such adhesion issues. In particular,the '190 application discloses golf balls wherein an aspherical hollowspace can be created within the core without using an insert, whichprior golf balls had incorporated to create the aspherical hollowcenter. One problem encountered with the prior golf balls incorporatinginserts to create an aspherical hollow space within the core was thatpoor bonding/adhesion sometimes occurred between the insert and anadjacent surrounding layer, resulting in separation of outer layer fromthe insert when the golf ball was struck by a club face. In golf ballsof the '190 application, a plurality of extensions of the shell layeradvantageously border and define the aspherical shape of the hollowspace within the core. Accordingly, any adhesion problems previouslyencountered between the insert and outer layer are totally eliminated.

However, there still remains a need for versatile and cost effectivehollow core golf ball constructions that can be implemented in sphericaland aspherical hollow core designs alike to produce excellent adhesiontherein. Such constructions, which meanwhile target desired playingcharacteristics and feel with excellent continuity of hardnessdistribution from the hollow interior radially outward, would beparticularly desirable. The golf balls of the invention address andsolve all of these needs.

SUMMARY OF THE INVENTION

Accordingly, a golf ball of the invention incorporates a hollowinnermost portion that may be spherical or aspherical, and displaysexcellent adhesion between layers with desirable continuity of hardnessdistribution from the innermost hollow portion outward toward the golfball outermost surface. Advantageously, the shell layer of a golf ballof the invention is at least partially non-continuous and has aplurality of hollow spaces therein, with each hollow space extendingfrom an inner surface to an outer surface of the shell layer, and thehollow spaces being symmetrically spaced within the shell layer.

The non-continuous shell layer has a first hardness gradient from shelllayer inner surface to outer surface of up to about 7 Shore C. And anouter core layer has a second hardness gradient and is formed about theouter surface and within the plurality of hollow spaces. The outer corelayer has a second inner surface having a second inner surface hardnessthat differs from the inner surface hardness. Thus, the second innersurface hardness and inner surface hardness may alternate symmetricallyand circumferentially about the innermost spherical hollow portion.These and other elements of a golf ball of the invention as followsmeanwhile target desired playing characteristics and feel.

In a first embodiment, the golf ball comprises a hollow core comprisingan innermost spherical hollow portion having a diameter of about 0.15inches to about 1.1 inches. A shell layer, surrounding the innermostspherical hollow portion, is formed from a thermoplastic composition andis at least partially non-continuous, having a plurality of hollowspaces therein that extend from an inner surface to an outer surface ofthe shell layer and are symmetrically spaced within the shell layer.That is, the plurality of hollow spaces are symmetrically positionedwithin and throughout the shell layer from inner surface to outersurface such that uniform flight and roll occur when the finished golfball is struck by a club face.

The inner surface has an inner surface hardness and the outer surfacehas an outer surface hardness that is greater than the inner surfacehardness by up to about 7 Shore C to define a first hardness gradient.The first hardness gradient in one embodiment may alternatively be about1 to 5 Shore C.

Meanwhile, at least one outer core layer, formed from a thermosetcomposition and having a second hardness gradient, is formed about theouter surface and within the plurality of hollow spaces. The outer corelayer has a second inner surface having a second inner surface hardnessthat differs from the inner surface hardness. In one embodiment, thesecond hardness gradient is a negative hardness gradient of about 3 to25 Shore C. In another embodiment, the second hardness gradient is apositive hardness gradient of about 3 to 25 Shore C.

Thus, the second inner surface hardness and inner surface hardnessalternate symmetrically and circumferentially about the innermostspherical hollow portion and adjacent thereto.

Many suitable patterns and designs are envisioned for the non-continuousshell layer—for example, the shell layer may simply be perforated. Inone embodiment, the shell layer is a screen. In another embodiment, theshell layer is a lattice.

At least one cover layer is disposed about the at least one outer corelayer. In one embodiment, the cover comprises an inner cover layerdisposed about the outer core layer and comprising an ionomeric materialand having a first hardness; and an outer cover layer disposed about theinner cover layer and comprising a polyurea or a polyurethane and havinga second hardness less than the first.

In one embodiment, the golf ball may further comprise a thermoplasticintermediate core layer that is disposed between the shell layer and theouter core layer and comprises a thermoplastic composition that isdifferent than the thermoplastic composition of the shell layer.

Alternatively, the golf ball may comprise a thermoset intermediate corelayer that is disposed between the shell layer and the outer core layerand comprises a thermoset composition that is different than thethermoset composition of the outer core layer; wherein the surfacehardness is greater than the inner surface hardness by about 3 to 25Shore C. For example, the thermoset composition of the outer core layermay comprise a thermoset rubber composition whereas the thermosetintermediate core layer comprises a different thermoset composition.

In a second embodiment, the shell layer is formed from a first thermosetrubber composition; and at least one outer core layer is formed from asecond thermoset composition disposed about the shell layer. The shelllayer has an inner surface having an inner surface hardness and an outersurface having an outer surface hardness greater than the inner surfacehardness by about 3 to 25 Shore C to define a first hardness gradient.And the outer core layer has a second hardness gradient different fromthe first hardness gradient.

In one embodiment, the second hardness gradient is about 0 Shore C. Inanother embodiment, the second hardness gradient is a negative hardnessgradient of about 2 to 25 Shore C. In yet another embodiment, the secondhardness gradient is a positive hardness gradient of about 3 to 10 ShoreC.

The golf ball may further comprise a thermoplastic intermediate corelayer disposed between the shell layer and the outer core layer; whereinthe inner cover layer has a material hardness greater than about 60Shore D; and wherein the outer cover layer has a material hardness ofless than about 60 Shore D; and wherein the surface hardness is greaterthan the inner surface hardness by about 10 to 25 Shore C.

Alternatively, the golf ball may further comprise a thermosetintermediate core layer disposed between the shell layer and the outercore layer comprising a third thermoset rubber composition differentfrom the first and the second; wherein the surface hardness is greaterthan the inner surface hardness by about 10 to 25 Shore C.

In a third embodiment, the shell layer is formed from a thermoset rubbercomposition; and at least one outer core layer is formed from athermoplastic composition disposed about the shell layer. The shelllayer has an inner surface having an inner surface hardness and an outersurface having an outer surface hardness greater than the inner surfacehardness by about 3 to 25 Shore C to define a first hardness gradient.And the outer core layer has a second hardness gradient.

In one embodiment, the second hardness gradient is about 0 Shore C. Inanother embodiment, the second hardness gradient is a negative hardnessgradient of about 1 to 10 Shore C. In yet another embodiment, the secondhardness gradient is a positive hardness gradient of about 1 to 10 ShoreC.

The golf ball may further comprise a thermoplastic intermediate corelayer disposed between the shell layer and the outer core layercomprising a thermoplastic composition that is different than thethermoplastic composition of the outer core layer; wherein the innercover layer has a material hardness greater than about 60 Shore D; andwherein the outer cover layer has a material hardness of less than about60 Shore D; and wherein the surface hardness is greater than the innersurface hardness by about 3 to 25 Shore C.

Alternatively, the golf ball may further comprise a thermosetintermediate core layer disposed between the shell layer and the outercore layer comprising a thermoset composition that is different than thethermoset rubber composition of the shell layer; wherein the surfacehardness is greater than the inner surface hardness by about 3 to 25Shore C.

In a fourth embodiment, the shell layer may be formed from a firstthermoplastic composition; and at least one outer core layer formed froma second thermoplastic composition disposed about the shell layer. Theshell layer has an inner surface having an inner surface hardness and anouter surface having an outer surface hardness greater than the innersurface hardness by up to about 7 Shore C to define a first hardnessgradient. And the outer core layer has a second hardness gradientdifferent from the first hardness gradient.

The golf ball may further comprise a thermoplastic intermediate corelayer that is disposed between the shell layer and the outer core layerand comprises a third thermoplastic composition different from the firstand the second.

Alternatively, the golf ball may further comprise a thermosetintermediate core layer that is disposed between the shell layer and theouter core layer and comprises a thermoset composition.

In a fifth embodiment, the shell layer may be formed from a firstthermoset composition; and at least one outer core layer formed from asecond thermoset composition disposed about the shell layer. The shelllayer has an inner surface having an inner surface hardness and

an outer surface has an outer surface hardness greater than the innersurface hardness by about 10 to 25 Shore C to define a first hardnessgradient; and the outer core layer has a second hardness gradientdifferent from the first hardness gradient.

In each of these embodiments, the spherical hollow portion mayalternatively have a diameter of about 0.20 inches to about 1.1 inches,or of about 0.20 inches to about 0.90 inches, or of about 0.25 inches toabout 1.1 inches. And the cover may have one or more layers as definedherein.

Furthermore, the outer surface hardness may in one embodiment be greaterthan about 55 Shore C.

Moreover, the shell layer may have a coefficient of restitution lessthan about 0.700 when measured at an incoming velocity of 125 ft/s. Anda combination of the shell layer and the outer core layer may have acoefficient of restitution (measured at an incoming velocity of 125ft/s) that is higher than the coefficient of restitution (also measuredat an incoming velocity of 125 ft/s) of the shell layer by 10-50%.

In one embodiment, the inner cover has a hardness of greater than about60 Shore D and the outer cover layer has a hardness of less than about60 Shore D. And the golf ball may have a first volume, and the sphericalhollow portion have a second volume that is about 2% to 30% of the firstvolume.

Advantageously, a golf ball of the invention may also be constructed totarget desired playing characteristics and feel yet create excellentadhesion between layers and continuity of hardness distribution inaspherical hollow core golf balls.

In a first embodiment, the golf ball comprises a core, and one or morecover layers. The core comprises an innermost aspherical hollow portion,a shell layer, and one or more outer core layers. The innermostaspherical hollow portion has a volume V_(ahp). The shell layer isformed from a thermoplastic composition and has an inner surfacecomprising a plurality of symmetrically spaced extensions that borderand define a shape of the innermost aspherical hollow portion. Theplurality of extensions and innermost aspherical hollow portion,combined, form a phantom sphere having a diameter of from about 0.15inches to about 1.1 inches. And the plurality of extensions have acombined total volume E_(TV) such that V_(ahp)≧E_(TV)>0.20(E_(TV)+V_(ahp)).

Meanwhile, the shell layer is also non-continuous, having a plurality ofhollow spaces therein that extend from the inner surface to an outersurface of the shell layer and are symmetrically spaced within the shelllayer surface.

Additionally, the inner surface has an inner surface hardness and theouter surface has an outer surface hardness greater than the innersurface hardness by up to about 7 Shore C to define a first hardnessgradient; and the outer core layer has a second hardness gradient.

The aspherical hollow portion has a shape that is axially symmetric. Theaspherical hollow portion may be at least one of non-spherical orirregularly-shaped.

The plurality of extensions and innermost aspherical hollow portion,combined, may alternatively form a spherical phantom sphere having adiameter of from about 0.30 inches to about 0.90 inches.

At least one outer core layer is formed about the outer surface. In oneembodiment, the outer core layer is formed from a thermoset composition.In another embodiment, the at least one outer core layer is formed froma thermoplastic composition.

The outer core layer has a second inner surface having a second innersurface hardness that differs from the inner surface hardness. Thus, thesecond inner surface hardness and inner surface hardness alternatesymmetrically and circumferentially about and adjacent to the innermostaspherical hollow portion.

The first hardness gradient may alternatively be about lto 5 Shore C.

The shell layer may be perforated, for example. In one embodiment, theshell layer is a screen. In another embodiment, the shell layer is alattice.

The innermost aspherical hollow portion, shell layer and outer corelayer, combined, may have an outer diameter of from about 0.75 inches toabout 1.62 inches, for example. The second hardness gradient may be anegative hardness gradient of about 3 to 25 Shore C. Alternatively, thesecond hardness gradient may be a positive hardness gradient of about 3to 25 Shore C.

That is, the plurality of extensions have a combined volume E_(TV) thatis equal to or less than volume V_(ahp) of the innermost asphericalhollow portion but greater than 20% of the total volume E_(TV)+V_(ahp)of the plurality of extensions and innermost aspherical hollow portion,combined.

Herein, the phantom sphere has a volume that is defined by the maximumradial distance of the innermost aspherical hollow portion. In golfballs of the invention, the shell layer may have a maximum thickness,including extensions, of up to about 0.40 inches, as long as thecombined volume E_(TV) of the extensions is such thatV_(ahp)≧E_(TV)>0.20(E_(TV)+V_(ahp)). In an alternative embodiment, thecombined volume E_(TV) of the extensions is such thatV_(ahp)≧E_(TV)>0.30(E_(TV)+V_(ahp)).

And the shell layer thickness at locations not containing extensions isless than the maximum thickness, with the extensions being sized andshaped such that their combined volume E_(TV) satisfy the relationshipV_(ahp)≧E_(TV)>0.20(E_(TV)+V_(ahp)). The shell layer may have asubstantially uniform thickness at locations not containing extensions.

In one embodiment, the at least one cover layer comprises an inner coverlayer disposed about the outer core layer, and an outer cover layerdisposed about the inner cover layer, wherein the inner cover layercomprises an ionomeric material and has a first hardness and the outercover layer comprises a polyurea or a polyurethane and has a secondhardness less than the first.

In a second embodiment, the shell layer is formed from a first thermosetrubber composition; and at least one outer core layer is formed from asecond thermoset composition disposed about the shell layer. The shelllayer has an inner surface having an inner surface hardness and an outersurface having an outer surface hardness greater than the inner surfacehardness by about 3 to 25 Shore C to define a first hardness gradient.And the outer core layer has a second hardness gradient different fromthe first hardness gradient.

In one embodiment, the second hardness gradient is about 0 Shore C. Inanother embodiment, the second hardness gradient is a negative hardnessgradient of about 2 to 25 Shore C. In yet another embodiment, the secondhardness gradient is a positive hardness gradient of about 3 to 10 ShoreC.

The golf ball may further comprise a thermoplastic intermediate corelayer disposed between the shell layer and the outer core layer; whereinthe inner cover layer has a material hardness greater than about 60Shore D; and wherein the outer cover layer has a material hardness ofless than about 60 Shore D; and wherein the surface hardness is greaterthan the inner surface hardness by about 10 to 25 Shore C.

Alternatively, the golf ball may further comprise a thermosetintermediate core layer disposed between the shell layer and the outercore layer comprising a third thermoset rubber composition differentfrom the first and the second; wherein the surface hardness is greaterthan the inner surface hardness by about 10 to 25 Shore C.

In a third embodiment, the shell layer is formed from a thermoset rubbercomposition; and at least one outer core layer is formed from athermoplastic composition disposed about the shell layer. The shelllayer has an inner surface having an inner surface hardness and an outersurface having an outer surface hardness greater than the inner surfacehardness by about 3 to 25 Shore C to define a first hardness gradient.And the outer core layer has a second hardness gradient.

In one embodiment, the second hardness gradient is about 0 Shore C. Inanother embodiment, the second hardness gradient is a negative hardnessgradient of about 1 to 10 Shore C. In yet another embodiment, the secondhardness gradient is a positive hardness gradient of about 1 to 10 ShoreC.

The golf ball may further comprise a thermoplastic intermediate corelayer disposed between the shell layer and the outer core layercomprising a thermoplastic composition that is different than thethermoplastic composition of the outer core layer; wherein the innercover layer has a material hardness greater than about 60 Shore D; andwherein the outer cover layer has a material hardness of less than about60 Shore D; and wherein the surface hardness is greater than the innersurface hardness by about 3 to 25 Shore C.

Alternatively, the golf ball may further comprise a thermosetintermediate core layer disposed between the shell layer and the outercore layer comprising a thermoset composition that is different than thethermoset rubber composition of the shell layer; wherein the surfacehardness is greater than the inner surface hardness by about 3 to 25Shore C.

In a fourth embodiment, the shell layer may be formed from a firstthermoplastic composition; and at least one outer core layer formed froma second thermoplastic composition disposed about the shell layer. Theshell layer has an inner surface having an inner surface hardness and anouter surface having an outer surface hardness greater than the innersurface hardness by up to about 7 Shore C to define a first hardnessgradient. And the outer core layer has a second hardness gradientdifferent from the first hardness gradient.

The golf ball may further comprise a thermoplastic intermediate corelayer that is disposed between the shell layer and the outer core layerand comprises a third thermoplastic composition different from the firstand the second.

Alternatively, the golf ball may further comprise a thermosetintermediate core layer that is disposed between the shell layer and theouter core layer and comprises a thermoset composition.

In a fifth embodiment, the shell layer may be formed from a firstthermoset composition; and at least one outer core layer formed from asecond thermoset composition disposed about the shell layer. The shelllayer has an inner surface having an inner surface hardness and an outersurface has an outer surface hardness greater than the inner surfacehardness by about 10 to 25 Shore C to define a first hardness gradient;and the outer core layer has a second hardness gradient different fromthe first hardness gradient.

In each of these embodiments, the spherical hollow portion mayalternatively have a diameter of about 0.20 inches to about 1.1 inches,or of about 0.20 inches to about 0.90 inches, or of about 0.25 inches toabout 1.1 inches. And the cover may have one or more layers as definedherein.

Furthermore, the outer surface hardness may in one embodiment be greaterthan about 55 Shore C.

Moreover, the shell layer may have a coefficient of restitution lessthan about 0.700 when measured at an incoming velocity of 125 ft/s. Anda combination of the shell layer and the outer core layer may have acoefficient of restitution (measured at an incoming velocity of 125ft/s) that is higher than the coefficient of restitution (also measuredat an incoming velocity of 125 ft/s) of the shell layer by 10-50%.

A golf ball of the invention may be alternatively constructed to targetdesired playing characteristics and feel yet create excellent adhesionbetween layers and continuity of hardness distribution in asphericalhollow center golf balls.

In a different embodiment of a golf ball incorporating an asphericalinnermost hollow portion, the golf ball comprises a core and one or morecover layers. The core comprises a shell layer that is formed from athermoplastic composition and has an inner surface comprising aplurality of symmetrically spaced extensions that border and define ashape of an innermost aspherical hollow portion. The innermostaspherical hollow portion comprises from about 2% to about 30% of atotal volume of the golf ball. The shell layer is at least partiallynon-continuous, having a plurality of hollow spaces therein that extendfrom the inner surface to an outer surface of the shell layer and aresymmetrically spaced within in the shell layer. At least one outer corelayer is formed about the outer surface.

The inner surface has an inner surface hardness and the outer surfacehas an outer surface hardness greater than the inner surface hardness byup to about 7 Shore C to define a first hardness gradient; and the outercore layer has a second hardness gradient.

The innermost aspherical hollow portion has a shape that is axiallysymmetric. The innermost aspherical hollow portion may be at least oneof non-spherical or irregularly-shaped.

The plurality of extensions and innermost aspherical hollow portion,combined, form a phantom sphere having a diameter of from about 0.15inches to about 1.1 inches.

The outer core layer has a second inner surface having a second innersurface hardness that differs from the inner surface hardness. Thus, thesecond inner surface hardness and inner surface hardness alternatesymmetrically and circumferentially about the innermost asphericalhollow portion.

In one embodiment, the first hardness gradient may be about 1 to 5 ShoreC.

The shell layer may be perforated. In one embodiment, the shell layer isa screen. In another embodiment the shell layer is a lattice.

The innermost aspherical hollow portion, shell layer and outer corelayer, combined, have an outer diameter of from about 0.75 inches toabout 1.62 inches.

The second hardness gradient may have a negative hardness gradient ofabout 3 to 25 Shore C. Alternatively, the second hardness gradient maybe a positive hardness gradient of about 3 to 25 Shore C.

In one embodiment, the at least one outer core layer is formed from athermoset composition. In another embodiment, the at least one outercore layer is formed from a thermoplastic composition.

In one embodiment, the at least one cover layer comprises an inner coverlayer disposed about the outer core layer, and an outer cover layerdisposed about the inner cover layer, wherein the inner cover layercomprises an ionomeric material and has a first hardness, and the outercover layer comprises a polyurea or a polyurethane and has a secondhardness less than the first.

In a second embodiment, the shell layer is formed from a first thermosetrubber composition; and at least one outer core layer is formed from asecond thermoset composition disposed about the shell layer. The shelllayer has an inner surface having an inner surface hardness and an outersurface having an outer surface hardness greater than the inner surfacehardness by about 3 to 25 Shore C to define a first hardness gradient.And the outer core layer has a second hardness gradient different fromthe first hardness gradient.

In one embodiment, the second hardness gradient is about 0 Shore C. Inanother embodiment, the second hardness gradient is a negative hardnessgradient of about 2 to 25 Shore C. In yet another embodiment, the secondhardness gradient is a positive hardness gradient of about 3 to 10 ShoreC.

The golf ball may further comprise a thermoplastic intermediate corelayer disposed between the shell layer and the outer core layer; whereinthe inner cover layer has a material hardness greater than about 60Shore D; and wherein the outer cover layer has a material hardness ofless than about 60 Shore D; and wherein the surface hardness is greaterthan the inner surface hardness by about 10 to 25 Shore C.

Alternatively, the golf ball may further comprise a thermosetintermediate core layer disposed between the shell layer and the outercore layer comprising a third thermoset rubber composition differentfrom the first and the second; wherein the surface hardness is greaterthan the inner surface hardness by about 10 to 25 Shore C.

In a third embodiment, the shell layer is formed from a thermoset rubbercomposition; and at least one outer core layer is formed from athermoplastic composition disposed about the shell layer. The shelllayer has an inner surface having an inner surface hardness and an outersurface having an outer surface hardness greater than the inner surfacehardness by about 3 to 25 Shore C to define a first hardness gradient.And the outer core layer has a second hardness gradient.

In one embodiment, the second hardness gradient is about 0 Shore C. Inanother embodiment, the second hardness gradient is a negative hardnessgradient of about 1 to 10 Shore C. In yet another embodiment, the secondhardness gradient is a positive hardness gradient of about 1 to 10 ShoreC.

The golf ball may further comprise a thermoplastic intermediate corelayer disposed between the shell layer and the outer core layercomprising a thermoplastic composition that is different than thethermoplastic composition of the outer core layer; wherein the innercover layer has a material hardness greater than about 60 Shore D; andwherein the outer cover layer has a material hardness of less than about60 Shore D; and wherein the surface hardness is greater than the innersurface hardness by about 3 to 25 Shore C.

Alternatively, the golf ball may further comprise a thermosetintermediate core layer disposed between the shell layer and the outercore layer comprising a thermoset composition that is different than thethermoset rubber composition of the shell layer; wherein the surfacehardness is greater than the inner surface hardness by about 3 to 25Shore C.

In a fourth embodiment, the shell layer may be formed from a firstthermoplastic composition; and at least one outer core layer formed froma second thermoplastic composition disposed about the shell layer. Theshell layer has an inner surface having an inner surface hardness and anouter surface having an outer surface hardness greater than the innersurface hardness by up to about 7 Shore C to define a first hardnessgradient. And the outer core layer has a second hardness gradientdifferent from the first hardness gradient.

The golf ball may further comprise a thermoplastic intermediate corelayer that is disposed between the shell layer and the outer core layerand comprises a third thermoplastic composition different from the firstand the second.

Alternatively, the golf ball may further comprise a thermosetintermediate core layer that is disposed between the shell layer and theouter core layer and comprises a thermoset composition.

In a fifth embodiment, the shell layer may be formed from a firstthermoset composition; and at least one outer core layer formed from asecond thermoset composition disposed about the shell layer. The shelllayer has an inner surface having an inner surface hardness and an outersurface has an outer surface hardness greater than the inner surfacehardness by about 10 to 25 Shore C to define a first hardness gradient;and the outer core layer has a second hardness gradient different fromthe first hardness gradient.

In each of these embodiments, the spherical hollow portion mayalternatively have a diameter of about 0.20 inches to about 1.1 inches,or of about 0.20 inches to about 0.90 inches, or of about 0.25 inches toabout 1.1 inches. And the cover may have one or more layers as definedherein.

Furthermore, the outer surface hardness may in one embodiment be greaterthan about 55 Shore C. Moreover, the shell layer may have a coefficientof restitution less than about 0.700 when measured at an incomingvelocity of 125 ft/s. And a combination of the shell layer and the outercore layer may have a coefficient of restitution (measured at anincoming velocity of 125 ft/s) that is higher than the coefficient ofrestitution (also measured at an incoming velocity of 125 ft/s) of theshell layer by 10-50%.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings form a part of the specification and are to beread in conjunction therewith. The illustrated embodiments, however, aremerely examples and are not intended to be limiting. Like referencenumerals and designations in the various drawings indicate likeelements.

FIG. 1 is an elevated exploded view of a non-continuous shell layeraccording to one embodiment of the invention;

FIG. 2 is an elevated view of a core of a golf ball or the inventionaccording to one embodiment;

FIG. 3 is an elevated view of a core of a golf ball or the inventionaccording to another embodiment;

FIG. 4 illustrates an outer core layer formed about a non-continuousshell layer and within a plurality of asymmetrically spaced hollowspaces of the non-continuous shell layer according to one embodiment ofthe invention; and

FIG. 5 is an elevated exploded view of a non-continuous shell layeraccording to one embodiment of the invention incorporating an asphericalinnermost hollow portion.

DETAILED DESCRIPTION OF THE INVENTION

Golf balls of the present invention may include multi-layer golf balls,such as one having a core and a cover surrounding the core, but arepreferably formed from a core having a hollow core and at least oneouter core layer, an inner cover layer, and an outer cover layer. Any ofthe core or cover layers may include more than one layer. The coverlayer of the golf ball may be a single layer or formed of a plurality oflayers, such as an inner cover layer and an outer cover layer. Thehollow core comprises an innermost hollow portion that may be sphericalin some embodiments, or aspherical in other embodiments.

Advantageously, a golf ball of the invention incorporates anon-continuous shell layer—that is, it contains a plurality ofspaces—perforations or other recesses—which extend from an inner surfaceof the shell layer to its outer surface. The inner surface has an innersurface hardness and the outer surface has an outer surface hardnessgreater than the inner surface hardness by up to about 7 Shore C todefine a first hardness gradient; and the outer core layer has a secondhardness gradient and is formed about the outer surface as well aswithin the plurality of hollow spaces.

The outer core layer has a second inner surface having a second innersurface hardness that differs from the inner surface hardness. Thus, theinnermost hollow portion of the golf ball may be immediately surrounded,encased or formed and shaped by the shell layer material, having theinner surface hardness, and the outer core layer material, being formedwithin the hollow spaces of the shell layer and having the second innersurface hardness.

Many different patterns/designs are envisioned as being suitable forforming the non-continuous shell layer, as long as the resulting shelllayer, with outer core layer material formed within the plurality ofspaces, is symmetrically disposed about the innermost hollow portion soas to ensure uniform golf ball flight and roll. This arrangement permitsvarying hardnesses to occur immediately surrounding the innermost hollowportion, thereby creating excellent continuity of hardness distributionwithin the hollow center golf ball while meanwhile providing excellentadhesion between the shell layer and surrounding outer core layer in ahollow core golf ball construction. For additional examples and detailssuitable for a golf ball of the invention, see for example, relatedapplications U.S. patent application Ser. No. 14/959,190, filed on Dec.4, 2015, and also a continuation-in-part of U.S. patent application Ser.Nos. 13/736,993, 13/736,997, 13/737,026, and 13/737,041, each filed onJan. 9, 2013, and incorporated herein by reference in their entireties,including all figures thereof.

FIGS. 1-5 highlight some of the features of a golf ball of the inventionand should not be construed as limiting the scope of the invention. FIG.1 illustrates a partial elevated exploded view of one possible corearrangement for a golf ball of the invention incorporating a sphericalinnermost hollow portion. Referring to FIG. 1, core 2 includes innermostspherical hollow portion 4, surrounded by shell layer 6, which in turnis surrounded by outer core layer 8. Shell layer 6 is non-continuous,having a plurality of symmetrically spaced hollow spaces 10 therein.Shell layer 6 has an inner surface 12 having an inner surface hardnessand an outer surface 14 having an outer surface hardness. The outersurface hardness is greater than the inner surface hardness to define afirst hardness gradient of from about 1 to 7 Shore C.

Outer core layer 8 has a second inner surface 16 which forms about shelllayer 6 as well as within the plurality of symmetrically spaced hollowspaces 10. Second inner surface 16 has a second inner surface hardnessthat differs from the inner surface hardness. Both inner surface 12 andsecond inner surface 16 are at least in part adjacent to and in contactwith innermost spherical hollow portion 4. The inner surface hardnessand second inner surface hardness can be coordinated to target excellentcontinuity of hardness distribution from innermost hollow portion,having zero hardness, outward.

Meanwhile, outer core layer 8 further has a second outer surface 18having a second outer surface hardness, and a second hardness gradientis defined by a difference in hardness between second outer surface 18and second inner surface 16.

FIG. 2 illustrates a partial elevated view of a core construction ofgolf ball of the invention incorporating one possible non-continuousouter shell layer construction. Referring to FIG. 2, core 20 includesinnermost spherical hollow portion 22 which is encased/surrounded and/orformed by shell layer 24 and partially visible through plurality ofsymmetrically spaced hollow spaces 26 of shell layer 24. Outer corelayer 28 is formed about an outer surface 30 of shell layer 24 andwithin the plurality of symmetrically spaced hollow spaces 26.

FIG. 3 illustrates a partial elevated view of a different possible coreconstruction incorporating a non-continuous outer shell layer; and FIG.4 is a partial elevated exploded view illustrating how the outer corelayer of FIG. 3 surrounds and can form within the shell layer. Referringto FIG. 3, core 32 includes an innermost spherical hollow portion 34that is encased by shell layer 36 and visible through a plurality ofsymmetrically spaced hollow spaces 38. Outer core layer 40 is formedabout an outer surface 42 of shell layer 36 and within the plurality ofsymmetrically spaced hollow spaces 38.

FIG. 4 emphasizes how in core 32, core layer 40 not only surrounds shelllayer 36 but also fills the plurality of symmetrically spaced hollowspaces 38 such that innermost spherical hollow portion 34 is adjacent toand surrounded by both the material of shell layer 36 and outer corelayer40, each having an inner surface 44 and second inner surface 46,respectively. Inner surface 44 has an inner surface hardness thatdiffers from a second inner surface hardness of second inner surfaces46. Outer surface 42 has an outer surface hardness that is greater thanthe inner surface hardness to define a first hardness gradient of fromabout 1 to 7 Shore C. And second outer surface 48 of outer core layer 40has a second outer surface hardness that differs from the second innersurface hardness to define a second hardness gradient.

FIG. 5 illustrates a partial elevated exploded view of one possible corearrangement for a golf ball of the invention incorporating an asphericalinnermost hollow portion. Referring to FIG. 5, core 50 includesinnermost aspherical hollow portion 52, formed by shell layer 54, aboutwhich outer core layer 56 is disposed. Shell layer 54 is non-continuous,having a plurality of symmetrically spaced hollow spaces 58 therein.Shell layer 54 also has an inner surface 60 having a plurality ofsymmetrically spaced extensions 62 that border and define the shape ofinnermost aspherical hollow portion 52. Inner surface 60 of shell layer54 has an inner surface hardness, and an outer surface 64 of shell layer54 has an outer surface hardness. The outer surface hardness is greaterthan the inner surface hardness to define a first hardness gradient offrom about 1 to 7 Shore C. Outer core layer 56 is formed about outersurface 56 as well as within the plurality of symmetrically spacedhollow spaces 58. And a second inner surface hardness of outer corelayer 56 differs from a second outer surface hardness of outer corelayer 56 to define a second hardness gradient.

Alternating hardnesses can therefore be symmetrically set about andadjacent to the innermost hollow portion of the core, which can createunique playing characteristics, excellent adhesion between layers andalso excellent continuity of hardness distribution from innermost hollowportion and radially outward.

In one embodiment, the hollow core of a golf ball of the inventionincludes a thermoset non-continuous shell layer containing or encasingthe innermost spherical hollow portion. In one embodiment, the thermosetshell layer is surrounded by at least two outer core layers, where oneouter core layer is formed from a thermoset material, and anintermediate core layer, disposed between the shell layer and the outercore layer, is formed from a thermoplastic material. In anotherembodiment, the thermoset shell layer is surrounded by at least twoouter core layers, where one outer core layer is formed from a thermosetmaterial, and an intermediate core layer, disposed between the shelllayer and the outer core layer, is formed from a thermoset material. Inyet another embodiment, the thermoset shell layer is surrounded by atleast two outer core layers, where one outer core layer is formed from athermoplastic material, and an intermediate core layer, disposed betweenthe shell layer and the outer core layer, is formed from a thermoplasticmaterial. In still another embodiment, the thermoset shell layer issurrounded by at least two outer core layers, where one outer core layeris formed from a thermoplastic material, and an intermediate core layer,disposed between the shell layer and the outer core layer, is formedfrom a thermoset material.

Alternatively, the non-continuous shell layer may comprise athermoplastic material. For example, in one embodiment, the hollow coreincludes a thermoplastic non-continuous shell layer containing orencasing the innermost spherical hollow portion. In one embodiment, thethermoplastic shell layer is surrounded by at least two outer corelayers, where one outer core layer is formed from a thermoset material,and an intermediate core layer, disposed between the shell layer and theouter core layer, is formed from a thermoplastic material. In anotherembodiment, the thermoplastic shell layer is surrounded by at least twoouter core layers, where one outer core layer is formed from a thermosetmaterial, and an intermediate core layer, disposed between the shelllayer and the outer core layer, is also formed from a thermosetmaterial. In yet another embodiment, the thermoplastic shell layer issurrounded by at least two outer core layers, where one outer core layeris formed from a thermoplastic material, and an intermediate core layer,disposed between the shell layer and the outer core layer, is formedfrom a thermoplastic material. In still another embodiment, thethermoplastic shell layer is surrounded by at least two outer corelayers, where one outer core layer is formed from a thermoplasticmaterial, and an intermediate core layer, disposed between the shelllayer and the outer core layer, is formed from a thermoset material.

In one preferred embodiment, the golf ball includes a hollow core formedfrom a thermoset rubber shell layer encasing an innermost sphericalhollow portion. In this embodiment, a single outer core layer is formedaround the shell layer to create the hollow golf ball core. The outercore layer is also formed from a thermoset material, which may be thesame rubber composition as the shell layer but is preferably a differentthermoset rubber composition. A single cover layer or multiple coverlayers are formed over the hollow core. Preferably, an inner cover layerand an outer cover layer are formed over the outer core layer. In oneembodiment, the inner cover includes an ionomeric material and the outercover layer includes a polyurea or, preferably, a polyurethane. Theouter cover layer is typically softer than the inner cover layer, suchas where the inner cover has a hardness of greater than about 60 Shore Dand the outer cover layer has a hardness of less than about 60 Shore D.

In the above embodiment, the innermost spherical hollow portionpreferably has a diameter of about 0.51 to 1.1 inches. The surfacehardness of the shell layer may be greater than the inner surfacehardness by about 3 to 25 Shore C to define the first hardness gradient.In a preferred embodiment, the thermoset outer core layer has a hardnessgradient that is different from the hardness gradient of the thermosetshell layer. Most preferably, the shell layer has a surface hardnessgreater than about 55 Shore C.

The thermoset non-continuous shell layer has a coefficient ofrestitution (COR) less than about 0.750 when measured at an incomingvelocity of 125 ft/s. Preferably, the COR is less than about 0.700, morepreferably about 0.500 to 0.700, and most preferably about 0.600 to0.700. The overall hollow core (the combination of the thermoset shelllayer and the thermoset outer core layer) has a COR, measured at anincoming velocity of 125 ft/s, higher than the COR of the inner coreshell layer by greater than about 5%, more preferably about 10 to 50%,and most preferably about 15 to 30%.

In an alternative embodiment, the hardness gradient of the thermosetouter core layer has a ‘zero hardness gradient’. The zero hardnessgradient is typically about 0 Shore C (defined herein as ±2 Shore C).The hardness gradient of the thermoset outer core layer may also have a‘negative hardness gradient’, preferably about 3 to 25 Shore C, morepreferably about 5 to 20 Shore C, and most preferably about 8 to 15Shore C. The hardness gradient of the thermoset outer core layer mayalso have a ‘positive hardness gradient’, preferably about 3 to 25 ShoreC, more preferably about 5 to 20 Shore C, and most preferably about 8 to15 Shore C.

The golf ball has a first volume and the hollow center has a secondvolume. The volume of the hollow center is about 2% to 30% of the golfball volume, more preferably about 5% to 25% of the golf ball volume,and most preferably about 10% to 20% of the golf ball volume.

Examples of suitable hardness profiles for cores in golf balls of theinvention may be found in related U.S. patent application Ser. Nos.13/736,993, 13/736,997, 13/737,026, and 13/737,041, each filed on Jan.9, 201, and any accompanying FIGS. 1a and 1b thereof, all incorporatedby reference herein as stated further above.

Golf balls of the invention may also include an aspherical hollow volumein the center of the golf ball, formed by a shell layer that ismeanwhile non-continuous. In such a golf ball of the invention, theshell layer has a plurality of hollow spaces therein that extend from aninner surface to an outer surface of the shell layer, and meanwhile alsohas a plurality of extensions located on an inner surface that borderand define the shape of the aspherical hollow volume rather than aseparate insert having hollow spaces that form the aspherical hollowvolume. The plurality of extensions and innermost hollow portion,combined, form a phantom sphere having an aspherical hollow volumewithin. Manufacturing costs are meanwhile also reduced since anaspherical hollow core is constructed such that the aspherical hollowvolume and shell layer are unitary.

Accordingly, in one embodiment of a golf ball of the invention, the corecomprises: an innermost aspherical hollow portion having a volumeV_(ahp); a shell layer that is formed from a thermoplastic or thermosetcomposition and has an inner surface comprising a plurality ofsymmetrically spaced extensions that border and define the shape of theinnermost aspherical hollow portion; and at least one outer core layerformed from a thermoset or thermoplastic composition disposed about theshell layer. The plurality of extensions and innermost aspherical hollowportion, combined, form a phantom sphere having a diameter of from about0.10 inches to about 1.1 inches; and the plurality of extensions have acombined total volume E_(TV) such thatV_(ahp)≧E_(TV)>0.20(E_(TV)+V_(ahp)). As defined above, the plurality ofextensions have a combined volume E_(TV) that is equal to or less thanvolume V_(ahp) of the innermost aspherical hollow portion but greaterthan 20% of the total volume E_(TV)+V_(ahp) of the plurality ofextensions and innermost aspherical hollow portion, combined.

In alternative embodiments, the combined volume E_(TV) of the extensionsmay be such that V_(ahp)≧E_(TV)>0.25(E_(TV)+V_(ahp)), orV_(ahp)≧E_(TV)>0.30(E_(TV)+V_(ahp)), orV_(ahp)≧E_(TV)>0.35(E_(TV)+V_(ahp)), orV_(ahp)≧E_(TV)>0.40(E_(TV)+V_(ahp)), orV_(ahp)≧E_(TV)>0.45(E_(TV)+V_(ahp)). In still other embodiments,V_(ahp)≧E_(TV)>˜0.20(E_(TV)+V_(ahp)),V_(ahp)≧E_(TV)>˜0.25(E_(TV)+V_(ahp)), orV_(ahp)≦E_(TV)>˜0.30(E_(TV)+V_(ahp)), orV_(ahp)≧E_(TV)>˜0.35(E_(TV)+V_(ahp)), orV_(ahp)˜E_(TV)>˜0.40(E_(TV)+V_(ahp)), orV_(ahp)≧E_(TV)>˜0.45(E_(TV)+V_(ahp)).

The plurality of extensions and innermost aspherical hollow portion,combined, form a phantom sphere having a volume that is defined by themaximum radial distance of the innermost aspherical hollow portion. Thediameter of the phantom sphere may alternatively be from about 0.20inches to about 1.1 inches, or from about 0.20 inches to about 0.90inches, or from about 0.25 inches to about 0.75 inches, or from about0.30 inches to about 0.50 inches, or from about 0.20 inches to about 1.0inches, or from about 0.25 inches to about 0.90 inches, or from about0.30 inches to about 0.90 inches. In one embodiment, the plurality ofextensions and innermost aspherical hollow portion, combined, has adiameter of greater than 0.5 inches, or greater than about 1.0 inches.

Meanwhile, the shell layer is at least partially non-continuous, havinga plurality of hollow spaces therein that extend from the inner surfaceto an outer surface of the shell layer and are symmetrically spacedwithin the shell layer. Additionally, the inner surface has an innersurface hardness and the outer surface has an outer surface hardnessgreater than the inner surface hardness by up to about 7 Shore C todefine a first hardness gradient; and the outer core layer has a secondhardness gradient.

The shell layer may have a maximum thickness, including extensions, ofup to about 0.40 inches, or up to about 0.375 inches, or up to about0.30 inches, or up to about 0.275 inches, or up to about 0.200 inches,or up to about 0.175 inches. In one embodiment, wherein the shell layeris relatively thick, the shell layer maximum thickness is from about0.125 inches to about 0.375 inches, or from about 0.2 inches to about0.3125 inches, or from about 0.25 inches to about 0.3 inches, or fromabout 0.26 inches to about 0.275 inches.

In some embodiments, the shell layer may have a thickness at locationsnot containing extensions of greater than about 0.01 inches but lessthan the maximum thickness. When the shell layer is desired to berelatively thin at locations not containing extensions, that thicknessmay be from about 0.01 inches to about 0.1 inches, or from about 0.02inches to about 0.075 inches, or from about 0.025 inches to about 0.04inches, or from about 0.03 inches to about 0.035 inches.

When the shell layer is relatively thin and formed from a thermoplasticmaterial, the thermoplastic material is preferably selected to besomewhat heat resistant (or blended with a heat resistant thermoplasticmaterial) to avoid melting of the layer by subsequent molding ofadditional core and/or cover layers.

With the dimensions of the hollow interior in mind, the hollow cores(innermost aspherical hollow portion, shell layer and outer corelayer(s)) of the invention may have an outer diameter of about 0.75inches to about 1.62 inches, or about 0.75 inches to about 1.58 inches,or about 1.0 inches to about 1.57 inches, or about 1.3 inches to about1.56 inches, or about 1.4 inches to about 1.55 inches. The shell layermay have an outer diameter of about 0.75 inches, 1.0 inches, 1.20inches, or 1.30 inches, with one outer diameter being 0.75 inches, or1.0 inches.

In an alternative embodiment, the outer core layer should have an outerdiameter (the entire hollow core, shell layer plus outer core layer) ofabout 1.30 inches to about 1.62 inches, or 1.4 inches to about 1.6inches, or about 1.5 inches to about 1.59 inches. In some embodiments,the outer core layer has an outer diameter of about 1.51 inches, 1.53inches, or 1.550 inches.

The inner and outer cover layers may for example have a thickness ofabout 0.010 to 0.080 inches, or about 0.015 to 0.060 inches, or about0.020 to 0.040 inches. Alternatively, the inner and outer cover layershave a thickness of about 0.015 inches to about 0.055 inches, or about0.02 inches to about 0.04 inches, or about 0.025 inches to about 0.035inches. The inner cover layer, if present, may have a hardness of about60 Shore D or greater, or about 65 Shore D or greater, or about 70 ShoreD or greater. The inner cover layer may harder than the outer coverlayer although embodiments are envisioned wherein the outer cover layeris harder than the inner cover layer. The outer cover layer may have ahardness of about 60 Shore D or less, or about 55 Shore D or less, orabout 50 Shore D or less.

FIGS. 1-6 of related U.S. patent application Ser. No. 14/959,190, filedon Dec. 4, 2015 (incorporated by reference herein in its entirety above)provide examples of some suitable constructions for shell layers formingaspherical innermost hollow portions, etc.

In golf balls of the present invention, any of the core, cover, orintermediate layer may include more than one layer.

In one embodiment, the hollow core is formed of a thermoset shell layerthat borders and defines the innermost aspherical hollow portion. Inanother embodiment, the hollow core is formed from a thermoset shelllayer and at least two outer core layers, wherein an outer core layer isformed from a thermoset material, and an intermediate core layer,disposed between the shell layer and the outer core layer, is formedfrom a thermoplastic material. In an alternative embodiment, the hollowcore includes a thermoset shell layer and at least two outer corelayers, wherein an outer core layer is formed from a thermoset material,and an intermediate core layer, disposed between the shell layer and theouter core layer, is formed from a thermoset material.

The hollow core may alternatively be formed of a thermoplastic shelllayer that borders and defines the shape of the innermost asphericalhollow portion. In another embodiment, the hollow core includes thethermoplastic shell layer and at least two outer core layers, wherein anouter core layer is formed from a thermoplastic material, and anintermediate core layer, disposed between the shell layer and the outercore layer, is formed from a thermoset material. In an alternativeembodiment, the hollow core includes the thermoplastic shell layer andat least two outer core layers, wherein an outer core layer is formedfrom a thermoplastic material, and an intermediate core layer, disposedbetween the shell layer and the outer core layer, is formed from athermoplastic material.

The shell, outer core, or intermediate core layers may have either aconventional “hard-to-soft” hardness gradient (i.e., the outermostsurface/portion of the layer is harder than the innermostsurface/portion), known as a “positive hardness gradient,” or a“soft-to-hard” hardness gradient (i.e., a “negative” hardness gradient)as measured radially-inward from the outer surface or portion of eachcomponent towards the innermost portion (i.e., from the outersurface/portion towards the inner surface/portion of the shell and/orcore layers). As used herein, the terms “negative” and “positive,” withrespect to hardness gradient, refer to the result of subtracting thehardness value at the innermost portion of the component being measured(e.g., the inner surface of a core layer) from the hardness value at theouter surface of the component being measured (e.g., the outer surfaceof an outer core layer). For example, if the outer surface of a corelayer has a lower hardness value than at the inner surface, the hardnessgradient will be deemed a “negative” gradient (a smaller number−a largernumber=a negative number), although the magnitude may be disclosed inthe application as the absolute value of the subtraction result incombination with the designation ‘negative’).

The thermoplastic shell, intermediate core layers, and outer core layersof the invention may have ‘positive hardness gradients’ or ‘negativehardness gradients’, as described above. Alternatively, thethermoplastic layers may have a ‘zero hardness gradient’, defined hereinto include a 0 Shore C hardness gradient±2 Shore C. The thermoplasticlayer ‘positive hardness gradient’ or ‘negative hardness gradient’ maybe from about 0 Shore C to about 10 Shore C, or about 2 Shore C to about8 Shore C, or about 3 Shore C to about 5 Shore C.

The thermoset shell, intermediate core layers, and outer core layers ofthe invention may have ‘positive hardness gradients’ or ‘negativehardness gradients’, as described above. Alternatively, the thermosetlayers may have a ‘zero hardness gradient’, defined herein to include a0 Shore C hardness gradient±2 Shore C. The thermoset layer ‘positivehardness gradient’ or ‘negative hardness gradient’ may be from about 1Shore C to about 30 Shore C, or about 2 Shore C to about 27 Shore C, orabout 5 Shore C to about 25 Shore C, or about 10 to 20 Shore C. Othersuitable thermoset ‘positive hardness gradient’ or ‘negative hardnessgradient’ core layers can be found in U.S. Pat. Nos. 7,537,529 and7,537,530, the disclosures of which are incorporated herein, in theirentirety, by reference thereto.

A variety of the above thermoset and thermoplastic hardness gradientlayers are envisioned and both ‘positive hardness gradients’ and/or‘negative hardness gradients’ may be combined to form the hollow coresof the invention having various layers of this nature.

The surface hardness of the shell or core layers is obtained from theaverage of a number of measurements taken from opposing hemispheres ofthe particular layer, taking care to avoid making measurements on theparting line or any surface defects, such as holes or protrusions.Hardness measurements are made pursuant to ASTM D-2240 “IndentationHardness of Rubber and Plastic by Means of a Durometer.” Because of thecurved surface of the hollow core or core layers, care must be taken toinsure that they are centered under the durometer indentor before asurface hardness reading is obtained. A calibrated, digital durometer,capable of reading to 0.1 hardness units is used for all hardnessmeasurements and is set to take hardness readings 1 second after themaximum reading is obtained. The digital durometer must be attached to,and its foot made parallel to, the base of an automatic stand, such thatthe weight on the durometer and attack rate conform to ASTM D-2240.

To prepare the hollow core for hardness and hardness gradientmeasurements, the core (shell layer or with one or two core layers) isgently pressed into a hemispherical holder having an internal diameterapproximately slightly smaller than the diameter of the core, such thatthe core is held in place in the hemispherical portion of the holderwhile concurrently leaving the geometric central plane of the coreexposed. The core is secured in the holder by friction, such that itwill not move during the cutting and grinding steps, but the friction isnot so excessive that distortion of the natural shape of the core wouldresult. The core is secured such that the parting line of the core isroughly parallel to the top of the holder. The diameter of the core ismeasured 90° to this orientation prior to securing. A measurement isalso made from the bottom of the holder to the top of the core toprovide a reference point for future calculations. A rough cut, madeslightly above the exposed geometric center of the core using a band sawor other appropriate cutting tool, making sure that the core does notmove in the holder during this step. The remainder of the core, still inthe holder, is secured to the base plate of a surface grinding machine.The exposed ‘rough’ core surface is ground to a smooth, flat surface,revealing the hollow portion of the core, which can be verified bymeasuring the height of the bottom of the holder to the exposed surfaceof the core, making sure that exactly half of the original height of thecore, as measured above, has been removed to within ±0.004 inches.

Leaving the core in the holder, the center of the core is found with acenter square and carefully marked and the hardness is measured at thecenter mark. Hardness measurements at any distance from the center ofthe core may be measured by drawing a line radially outward from thecenter mark, and measuring and marking the distance from the center,typically in 1- or 2-mm increments. All hardness measurements performedon the plane passing through the hollow portion are performed while thecore is still in the holder and without having disturbed itsorientation, such that the test surface is constantly parallel to thebottom of the holder. The hardness difference from any predeterminedlocation on the core is calculated as the average surface hardness minusthe hardness at the appropriate reference point.

One or more of the shell layer and/or core layers may be formed from acomposition including at least one thermoset base rubber, such as apolybutadiene rubber, cured with at least one peroxide and at least onereactive co-agent, which can be a metal salt of an unsaturatedcarboxylic acid, such as acrylic acid or methacrylic acid, anon-metallic coagent, or mixtures thereof. Preferably, a suitableantioxidant is included in the composition. An optional ‘soft and fastagent’ (sometimes called a cis-to-trans catalyst), such as anorganosulfur or metal-containing organosulfur or thiol compound, canalso be included in the core formulation. Other ingredients that areknown to those skilled in the art may be used, and are understood toinclude, but not be limited to, density-adjusting fillers, processaides, plasticizers, blowing or foaming agents, sulfur accelerators,and/or non-peroxide radical sources.

The base thermoset rubber, which can be blended with other rubbers andpolymers, typically includes a natural or synthetic rubber. For example,the base rubber can be 1,4-polybutadiene having a cis structure of atleast 40%, preferably greater than 80%, and more preferably greater than90%.

Examples of desirable polybutadiene rubbers include BUNA® CB22 and BUNA®CB23, CB1221, CB1220, CB24, and CB21, commercially-available fromLANXESS Corporation; UBEPOL® 360L and UBEPOL® 150L and UBEPOL-BRrubbers, commercially available from UBE Industries, Ltd. of Tokyo,Japan; KINEX® 7245, KINEX® 7265, and BUDENE 1207 and 1208, commerciallyavailable from Goodyear of Akron, Ohio; SE BR-1220; Europrene® NEOCIS®BR 40 and BR 60, commercially available from Polimeri Europa; and BR 01,BR 730, BR 735, BR 11, and BR 51, commercially available from JapanSynthetic Rubber Co., Ltd; PETROFLEX® BRNd-40; and KARBOCHEM® ND40,ND45, and ND60, commercially available from Karbochem.

From the Lanxess Corporation, are for example the Nd- and Co-catalyzedgrades, but all of the following may be used: BUNA CB 21; BUNA CB 22;BUNA CB 23; BUNA CB 24; BUNA CB 25; BUNA CB 29 MES; BUNA CB Nd 40; BUNACB Nd 40 H; BUNA CB Nd 60; BUNA CB 55 NF; BUNA CB 60; BUNA CB 45 B; BUNACB 55 B; BUNA CB 55 H; BUNA CB 55 L; BUNA CB 70 B; BUNA CB 1220; BUNA CB1221; BUNA CB 1203; BUNA CB 45. Additionally, numerous suitable rubbersare available from JSR (Japan Synthetic Rubber), UBEPOL sold by UbeIndustries Inc, Japan, BST sold by BST Elastomers, Thailand; IPCL soldby Indian Petrochemicals Ltd, India; NITSU sold by Karbochem orKarbochem Ltd of South Africa; PETROFLEX of Brazil; LG of Korea; andKuhmo Petrochemical of Korea.

The base rubber may also comprise high or medium Mooney viscosityrubber, or blends thereof. A “Mooney” unit is a unit used to measure theplasticity of raw or unvulcanized rubber and is defined according toASTM D-1646. The Mooney viscosity range may for example be greater thanabout 40, or in the range of from about 40 to 60, or in the range fromabout 40 to 52.

Commercial sources of suitable polybutadienes include Bayer AG CB23(Nd-catalyzed), which has a Mooney viscosity of around 50 and is ahighly linear polybutadiene, and CB 1221 (Co-catalyzed). If desired, thepolybutadiene can also be mixed with other elastomers known in the art,such as other polybutadiene rubbers, natural rubber, styrene butadienerubber, and/or isoprene rubber in order to further modify the propertiesof the core. When a mixture of elastomers is used, the amounts of otherconstituents in the core composition are typically based on 100 parts byweight of the total elastomer mixture.

In one embodiment, the base rubber comprises a Nd-catalyzedpolybutadiene, a rare earth-catalyzed polybutadiene rubber, or blendsthereof. If desired, the polybutadiene can also be mixed with otherelastomers known in the art such as natural rubber, polyisoprene rubberand/or styrene-butadiene rubber in order to modify the properties of thecore. Other suitable base rubbers include thermosetting materials suchas, ethylene propylene diene monomer rubber, ethylene propylene rubber,butyl rubber, halobutyl rubber, hydrogenated nitrile butadiene rubber,nitrile rubber, and silicone rubber.

Suitable peroxide initiating agents include dicumyl peroxide;2,5-dimethyl-2,5-di(t-butylperoxy) hexane;2,5-dimethyl-2,5-di(t-butylperoxy)hexyne;2,5-dimethyl-2,5-di(benzoylperoxy)hexane;2,2′-bis(t-butylperoxy)-di-iso-propylbenzene;1,1-bis(t-butylperoxy)-3,3,5-trimethyl cyclohexane; n-butyl4,4-bis(t-butyl-peroxy)valerate; t-butyl perbenzoate; benzoyl peroxide;n-butyl 4,4′-bis(butylperoxy) valerate; di-t-butyl peroxide; or2,5-di-(t-butylperoxy)-2,5-dimethyl hexane, lauryl peroxide, t-butylhydroperoxide, α-α bis(t-butylperoxy) diisopropylbenzene,di(2-t-butyl-peroxyisopropyl)benzene, di-t-amyl peroxide, di-t-butylperoxide. For example, the rubber composition may include from about0.25 to about 5.0 parts by weight peroxide per 100 parts by weightrubber (phr), or 0.5 phr to 3 phr, or 0.5 phr to 1.5 phr. In oneembodiment, the peroxide is present in an amount of about 0.8 phr. Theseranges of peroxide are given assuming the peroxide is 100% active,without accounting for any carrier that might be present. Because manycommercially available peroxides are sold along with a carrier compound,the actual amount of active peroxide present must be calculated.Commercially-available peroxide initiating agents include DICUP™ familyof dicumyl peroxides (including DICUP™ R, DICUP™ 40C and DICUP™ 40KE)available from Crompton (Geo Specialty Chemicals). Similar initiatingagents are available from AkroChem, Lanxess, Flexsys/Harwick and R.T.Vanderbilt. Another commercially-available initiating agent is TRIGONOX™265-50B from Akzo Nobel, which is a mixture of1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane anddi(2-t-butylperoxyisopropyl) benzene. TRIGONOX™ peroxides are generallysold on a carrier compound.

Suitable reactive co-agents include, but are not limited to, metal saltsof diacrylates, dimethacrylates, and monomethacrylates suitable for usein this invention include those wherein the metal is zinc, magnesium,calcium, barium, tin, aluminum, lithium, sodium, potassium, iron,zirconium, and bismuth. Zinc diacrylate (ZDA) is preferred, but thepresent invention is not limited thereto. ZDA provides golf balls with ahigh initial velocity. The ZDA can be of various grades of purity. Forthe purposes of this invention, the lower the quantity of zinc stearatepresent in the ZDA the higher the ZDA purity. ZDA containing less thanabout 10% zinc stearate is preferable. More preferable is ZDA containingabout 4-8% zinc stearate. Suitable, commercially available zincdiacrylates include those from Sartomer Co. Examples of concentrationsof ZDA that can be used are about 10 phr to about 40 phr, or 20 phr toabout 35 phr, or 25 phr to about 35 phr. In one embodiment, the reactiveco-agent is present in an amount of about 29 phr to about 31 phr.

Additional co-agents that may be used alone or in combination with thosementioned above include, but are not limited to, trimethylolpropanetrimethacrylate, trimethylolpropane triacrylate, and the like. It isunderstood by those skilled in the art, that in the case where theseco-agents may be liquids at room temperature, it may be advantageous todisperse these compounds on a suitable carrier to promote ease ofincorporation in the rubber mixture.

Antioxidants are compounds that inhibit or prevent the oxidativebreakdown of elastomers, and/or inhibit or prevent reactions that arepromoted by oxygen radicals. Some exemplary antioxidants that may beused in the present invention include, but are not limited to, quinolinetype antioxidants, amine type antioxidants, and phenolic typeantioxidants. A preferred antioxidant is2,2′-methylene-bis-(4-methyl-6-t-butylphenol) available as VANOX® MBPCfrom R.T. Vanderbilt. Other polyphenolic antioxidants include VANOX® T,VANOX® L, VANOX® SKT, VANOX® SWP, VANOX® 13 and VANOX® 1290.

Suitable antioxidants include, but are not limited to,alkylene-bis-alkyl substituted cresols; substituted phenols; alkylenebisphenols; and alkylene trisphenols. The antioxidant is typicallypresent in an amount of about 0.1 phr to 5 phr, or from about 0.1 phr to2 phr, or about 0.1 phr to 1 phr. In an alternative embodiment, theantioxidant should be present in an amount to ensure that the hardnessgradient of the core layers is “negative.” For example, about 0.2 phr to1 phr antioxidant may be added to the core layer formulation, or about0.3 to 0.8 phr, or 0.4 to 0.7 phr. About 0.25 phr to 1.5 phr of peroxideas calculated at 100% active can be added to the core formulation, orabout 0.5 phr to 1.2 phr, or about 0.7 phr to 1.0 phr. The ZDA amountcan be varied to suit the desired compression, spin and feel of theresulting golf ball. The cure regime can have a temperature range fromabout 290° F. to 350° F., or about 300° F. to 335° F., and the stock isheld at that temperature for about 10 minutes to 30 minutes foreexample.

The thermoset rubber compositions may also include an optional ‘soft andfast agent’. As used herein, “soft and fast agent” means any compound ora blend thereof that that is capable of making a core 1) be softer(lower compression) at constant COR or 2) have a higher COR at equalcompression, or any combination thereof, when compared to a coreequivalently prepared without a soft and fast agent. The thermoset corelayer compositions may for example contain about 0.05 phr to 10.0 phrsoft and fast agent. In one embodiment, the soft and fast agent ispresent in an amount of about 0.05 phr to 3.0 phr, or about 0.05 phr to2.0 phr, or about 0.05 phr to 1.0 phr. In another embodiment, the softand fast agent is present in an amount of about 2.0 phr to 5.0 phr, orabout 2.35 phr to 4.0 phr, or about 2.35 phr to 3.0 phr. Suitable softand fast agents include, but are not limited to, organosulfur ormetal-containing organosulfur compounds, an organic sulfur compound,including mono, di, and polysulfides, a thiol, or mercapto compound, aninorganic sulfide compound, a Group VIA compound, or mixtures thereof.The soft and fast agent component may also be a blend of an organosulfurcompound and an inorganic sulfide compound.

Fillers may be added to the thermoset rubber layer compositionstypically include, but are not limited to, processing aids and/orcompounds to affect rheological and mixing properties, density-modifyingfillers, tear strength, or reinforcement fillers, and the like. Fillersinclude materials such as tungsten, zinc oxide, barium sulfate, silica,calcium carbonate, zinc carbonate, metals, metal oxides and salts,regrind (recycled core material typically ground to about 30 meshparticle size), high-Mooney-viscosity rubber regrind, trans-rubberregrind (recycled core material containing high trans isomer ofpolybutadiene), and the like. When trans-regrind is present, the amountof trans isomer can preferably be between about 10% and 60%. The fillersare generally inorganic and suitable fillers include numerous metals ormetal oxides, such as zinc oxide and tin oxide, as well as bariumsulfate, zinc sulfate, calcium carbonate, barium carbonate, clay,tungsten, tungsten carbide, an array of silicas, and mixtures thereof.Fillers may also include various foaming agents or blowing agents whichmay be readily selected by one of ordinary skill in the art. Fillers mayinclude polymeric, ceramic, metal, and glass microspheres may be solidor hollow, and filled or unfilled. Fillers may be added to one or morelayers of the golf ball to modify the density thereof.

The thermoset rubber shell and/or core layers may optionally include atleast one additive and/or filler. These materials are also suitable forinclusion in the thermoplastic layers of the present invention. Suitableadditives and fillers include, but are not limited to, chemical blowingand foaming agents, optical brighteners, coloring agents, fluorescentagents, whitening agents, UV absorbers, light stabilizers, defoamingagents, processing aids, antioxidants, stabilizers, softening agents,fragrance components, plasticizers, impact modifiers, TiO₂, acidcopolymer wax, surfactants, performance additives (e.g., A-C performanceadditives, particularly A-C low molecular weight ionomers andcopolymers, A-C oxidized polyethylenes, and A-C ethylene vinyl acetatewaxes, commercially available from Honeywell International Inc.), fattyacid amides (e.g., ethylene bis-stearamide and ethylene bis-oleamide),fatty acids and salts thereof (e.g., stearic acid, oleic acid, zincstearate, magnesium stearate, zinc oleate, and magnesium oleate), andfillers, such as zinc oxide, tin oxide, barium sulfate, zinc sulfate,calcium oxide, calcium carbonate, zinc carbonate, barium carbonate,tungsten, tungsten carbide, silica, lead silicate, regrind, clay, mica,talc, nano-fillers, carbon black, glass flake, milled glass, flock,fibers, and mixtures thereof. Suitable additives are more fullydescribed in, U.S. Pat. No. 7,041,721 which issued on May 9, 2006, thedisclosure of which is hereby incorporated herein by reference. In aparticular embodiment, the total amount of additive(s) and filler(s)present in the particle composition is 20 wt % or less, or 15 wt % orless, or 12 wt % or less, or 10 wt % or less, or 9 wt % or less, or 6 wt% or less, or 5 wt % or less, or 4 wt % or less, or 3 wt % or less, orwithin a range having a lower limit of 0 or 2 or 3 or 5 wt %, based onthe total weight of the particle composition, and an upper limit of 9 or10 or 12or 15 or 20 wt %, based on the total weight of the particlecomposition. In a particular aspect of this embodiment, the particlecomposition includes fillers selected from carbon black, micro- andnano-scale clays and organoclays, including (e.g., CLOISITE and NANOFILnanoclays, commercially available from Southern Clay Products, Inc.;NANOMAX and NANOMER nanoclays, commercially available from Nanocor,Inc., and PERKALITE nanoclays, commercially available from Akzo NobelPolymer Chemicals), micro- and nano-scale talcs (e.g., LUZENAC HAR highaspect ratio talcs, commercially available from Luzenac America, Inc.),glass (e.g., glass flake, milled glass, microglass, and glass fibers),micro- and nano-scale mica and mica-based pigments (e.g., IRIODIN pearlluster pigments, commercially available from The Merck Group), andcombinations thereof. Particularly suitable combinations of fillersinclude, but are not limited to, micro-scale fillers combined withnano-scale fillers, and organic fillers with inorganic fillers.

Alternatively, the thermoset layers herein may be formed from acastable, pourable reactive material such as a castable polyurea or acastable polyurethane; castable hybrid poly(urethane/urea); and castablehybrid poly(urea/urethane). Suitable polyurethanes include for examplethose disclosed in U.S. Pat. Nos. 5,334,673 and 6,506,851. Suitablepolyureas include for example those disclosed in U.S. Pat. Nos.5,484,870 and 6,835,794. These patents are incorporated herein byreference thereto.

For the thermoset layers of the invention, the fillers and/or additivesare present in an amount of about 50 wt % or less, or 30 wt % or less,or 20 wt % or less, or 15 wt % or less, based on the total weight of thecomposition. Alternatively, for the thermoplastic layers of theinvention, the fillers and/or additives are present in an amount ofabout 10 wt % or less, or 6 wt % or less, or 3 wt % or less, based onthe total weight of the composition.

The particle composition optionally includes one or more melt flowmodifiers. Suitable melt flow modifiers include materials which increasethe melt flow of the composition, as measured using ASTM D-1238,condition E, at 190° C., using a 2160-g weight. Examples of suitablemelt flow modifiers include, but are not limited to, fatty acids andfatty acid salts, including, but not limited to, those disclosed in U.S.Pat. No. 5,306,760, the disclosure of which is hereby incorporatedherein by reference; fatty amides and salts thereof; polyhydricalcohols, including, but not limited to, those disclosed in U.S. Pat.Nos. 7,365,128 and 8,163,823, the entire disclosures of which are herebyincorporated herein by reference; polylactic acids, including, but notlimited to, those disclosed in U.S. Pat. No. 7,642,319, the disclosureof which is hereby incorporated herein by reference; and the modifiersdisclosed in U.S. Pat. No. 8,163,823 and U.S. Patent ApplicationPublication No. 2009/0203469, the disclosures of which are herebyincorporated herein by reference. Flow enhancing additives also include,but are not limited to, montanic acids, esters of montanic acids andsalts thereof, bis-stearoylethylenediamine, mono- and polyalcohol esterssuch as pentaerythritol tetrastearate, zwitterionic compounds, andmetallocene-catalyzed polyethylene and polypropylene wax, includingmaleic anhydride modified versions thereof, amide waxes and alkylenediamides such as bistearamides. Particularly suitable fatty amidesinclude, but are not limited to, saturated fatty acid monoamides (e.g.,lauramide, palmitamide, arachidamide behenamide, stearamide, and12-hydroxy stearamide); unsaturated fatty acid monoamides (e.g.,oleamide, erucamide, and ricinoleamide); N-substituted fatty acid amides(e.g., N-stearyl stearamide, N-behenyl behenamide, N-stearyl behenamide,N-behenyl stearamide, N-oleyl oleamide, N-oleyl stearamide, N-stearyloleamide, N-stearyl erucamide, erucyl erucamide, and erucyl stearamide,N-oleyl palmitamide, methylol amide (preferably methylol stearamide,methylol behenamide); saturated fatty acid bis-amides (e.g., methylenebis-stearamide, ethylene bis-stearamide, ethylene bis-isostearamide,ethylene bis-hydroxystearamide, ethylene bis-behenamide, hexamethylenebis-stearamide, hexamethylene bis-behenamide, hexamethylenebis-hydroxystearamide, N,N′-distearyl adipamide, and N,N′-distearylsebacamide); unsaturated fatty acid bis-amides (e.g., ethylenebis-oleamide, hexamethylene bis-oleamide, N,N′-dioleyl adipamide,N,N′-dioleyl sebacamide); and saturated and unsaturated fatty acid tetraamides, stearyl erucamide, ethylene bis stearamide and ethylene bisoleamide. Suitable examples of commercially available fatty amidesinclude, but are not limited to, KEMAMIDE fatty acids, such as KEMAMIDEB (behenamide/arachidamide), KEMAMIDE W40 (N,N′-ethylenebisstearamide),KEMAMIDE P181 (oleyl palmitamide), KEMAMIDE S (stearamide), KEMAMIDE U(oleamide), KEMAMIDE E (erucamide), KEMAMIDE O (oleamide), KEMAMIDE W45(N,N′-ethylenebisstearamide), KENAMIDE W20 (N,N′-ethylenebisoleamide),KEMAMIDE E180 (stearyl erucamide), KEMAMIDE E221 (erucyl erucamide),KEMAMIDE S180 (stearyl stearamide), KEMAMIDE 5221 (erucyl stearamide),commercially available from Chemtura Corporation; and CRODAMIDE fattyamides, such as CRODAMIDE OR (oleamide), CRODAMIDE ER (erucamide),CRODAMIDE SR (stereamide), CRODAMIDE BR (behenamide), CRODAMIDE 203(oleyl palmitamide), and CRODAMIDE 212 (stearyl erucamide), commerciallyavailable from Croda Universal Ltd.

The shell layer, and intermediate and outer core layers of the hollowgolf ball may also be formed from thermoplastic materials such asionomeric polymers, and highly- and fully-neutralized ionomers (HNP).Acid moieties of the HNP's, typically ethylene-based ionomers, can beneutralized greater than about 80%, or greater than about 90%, or evenabout 100% or greater. The HNP's can be also be blended with a secondpolymer component, which, if containing an acid group, may beneutralized in a conventional manner, by the organic fatty acids of thepresent invention, or both. The second polymer component, which may bepartially- or fully-neutralized, may comprise ionomeric copolymers andterpolymers, ionomer precursors, thermoplastics, polyamides,polycarbonates, polyesters, polyurethanes, polyureas, thermoplasticelastomers, polybutadiene rubber, balata, metallocene-catalyzed polymers(grafted and non-grafted), single-site polymers, high-crystalline acidpolymers, cationic ionomers, and the like. HNP polymers typically have amaterial hardness of between about 20 and about 80 Shore D, and aflexural modulus of between about 3,000 psi and about 200,000 psi.

The HNP's may be ionomers and/or their acid precursors that areneutralized, either fully or partially, with organic acid copolymers orthe salts thereof. The acid copolymers are often preferably α-olefin,such as ethylene, C₃₋₈ α,β-ethylenically unsaturated carboxylic acid,such as acrylic and methacrylic acid, copolymers. They may optionallycontain a softening monomer, such as alkyl acrylate and alkylmethacrylate, wherein the alkyl groups have from 1 to 8 carbon atoms.

The acid copolymers can be described as E/X/Y copolymers where E isethylene, X is an α,β-ethylenically unsaturated carboxylic acid, and Yis a softening comonomer. In a preferred embodiment, X is acrylic ormethacrylic acid and Y is a C₁₋₈ alkyl acrylate or methacrylate ester. Xis often preferably present in an amount from about 1 to about 35 weightpercent of the polymer, or from about 5 to about 30 weight percent ofthe polymer, or from about 10 to about 20 weight percent of the polymer.Y is often preferably present in an amount from about 0 to about 50weight percent of the polymer, or from about 5 to about 25 weightpercent of the polymer, or from about 10 to about 20 weight percent ofthe polymer.

Specific acid-containing ethylene copolymers include, but are notlimited to, ethylene/acrylic acid/n-butyl acrylate, ethylene/methacrylicacid/n-butyl acrylate, ethylene/methacrylic acid/iso-butyl acrylate,ethylene/acrylic acid/iso-butyl acrylate, ethylene/methacrylicacid/n-butyl methacrylate, ethylene/acrylic acid/methyl methacrylate,ethylene/acrylic acid/methyl acrylate, ethylene/methacrylic acid/methylacrylate, ethylene/methacrylic acid/methyl methacrylate, andethylene/acrylic acid/n-butyl methacrylate. Preferred acid-containingethylene copolymers include, ethylene/methacrylic acid/n-butyl acrylate,ethylene/acrylic acid/n-butyl acrylate, ethylene/methacrylic acid/methylacrylate, ethylene/acrylic acid/ethyl acrylate, ethylene/methacrylicacid/ethyl acrylate, and ethylene/acrylic acid/methyl acrylatecopolymers. The most preferred acid-containing ethylene copolymers are,ethylene/(meth) acrylic acid/n-butyl, acrylate, ethylene/(meth)acrylicacid/ethyl acrylate, and ethylene/(meth) acrylic acid/methyl acrylatecopolymers.

Ionomers are typically neutralized with a metal cation, such as Li, Na,Mg, K, Ca, or Zn. It has been found that by adding sufficient organicacid or salt of organic acid, along with a suitable base, to the acidcopolymer or ionomer, however, the ionomer can be neutralized, withoutlosing processability, to a level much greater than for a metal cation.The acid moieties may be neutralized greater than about 80%, or from90-100%, or 100% or greater without losing processability. Thisaccomplished by melt-blending an ethylene α,β-ethylenically unsaturatedcarboxylic acid copolymer, for example, with an organic acid or a saltof organic acid, and adding a sufficient amount of a cation source toincrease the level of neutralization of all the acid moieties (includingthose in the acid copolymer and in the organic acid) to greater than90%, or greater than 100%.

The organic acids are typically aliphatic, mono- or multi-functional(saturated, unsaturated, or multi-unsaturated) organic acids. Salts ofthese organic acids may also be employed. The salts of organic acids ofthe present invention include the salts of barium, lithium, sodium,zinc, bismuth, chromium, cobalt, copper, potassium, strontium, titanium,tungsten, magnesium, cesium, iron, nickel, silver, aluminum, tin, orcalcium, salts of fatty acids, particularly stearic, behenic, erucic,oleic, linoelic or dimerized derivatives thereof. It is preferred thatthe organic acids and salts of the present invention be relativelynon-migratory (they do not bloom to the surface of the polymer underambient temperatures) and non-volatile (they do not volatilize attemperatures required for melt-blending).

The ionomers of the invention may also be more conventional ionomers,i.e., partially-neutralized with metal cations. The acid moiety in theacid copolymer may be neutralized about 1 to about 90%, or at leastabout 20 to about 75%, or at least about 40 to about 70%, to form anionomer, by a cation such as lithium, sodium, potassium, magnesium,calcium, barium, lead, tin, zinc, aluminum, or a mixture thereof.

Examples of thermoplastic materials are disclosed in U.S. Pat. No.7,591,742, the disclosure of which is incorporated herein in itsentirety by reference thereto.

Thermoplastic elastomers (TPE) many also be used for the thermoplasticshell or core layers and/or to modify the properties of the shell and/orcore layers, or the uncured rubber core layer stock by blending with thebase thermoset rubber. These TPEs include natural or synthetic balata,or high trans-polyisoprene, high trans-polybutadiene, or any styrenicblock copolymer, such as styrene ethylene butadiene styrene,styrene-isoprene-styrene, etc., a metallocene or other single-sitecatalyzed polyolefin such as ethylene-octene, or ethylene-butene, orthermoplastic polyurethanes (TPU), including copolymers, e.g. withsilicone. Other suitable TPEs for blending with the thermoset rubbers ofthe present invention include PEBAX®, which is believed to comprisepolyether amide copolymers, HYTREL®, which is believed to comprisepolyether ester copolymers, thermoplastic urethane, and KRATON®, whichis believed to comprise styrenic block copolymers elastomers. Any of theTPEs or TPUs above may also contain functionality suitable for grafting,including maleic acid or maleic anhydride.

Additional polymers may also optionally be incorporated into the baserubber for the shell and core layers. Examples include, but are notlimited to, thermoset elastomers such as core regrind, thermoplasticvulcanizate, copolymeric ionomer, terpolymeric ionomer, polycarbonate,polyamide, copolymeric polyamide, polyesters, polyvinyl alcohols,acrylonitrile-butadiene-styrene copolymers, polyarylate, polyacrylate,polyphenylene ether, impact-modified polyphenylene ether, high impactpolystyrene, diallyl phthalate polymer, styrene-acrylonitrile polymer(SAN) (including olefin-modified SAN andacrylonitrile-styrene-acrylonitrile polymer), styrene-maleic anhydridecopolymer, styrenic copolymer, functionalized styrenic copolymer,functionalized styrenic terpolymer, styrenic terpolymer, cellulosepolymer, liquid crystal polymer, ethylene-vinyl acetate copolymers,polyurea, and polysiloxane or any metallocene-catalyzed polymers ofthese species.

Suitable polyamides for use as an additional polymeric material incompositions within the scope of the present invention also includeresins obtained by: (1) polycondensation of (a) a dicarboxylic acid,such as oxalic acid, adipic acid, sebacic acid, terephthalic acid,isophthalic acid, or 1,4-cyclohexanedicarboxylic acid, with (b) adiamine, such as ethylenediamine, tetramethylenediamine,pentamethylenediamine, hexamethylenediamine, or decamethylenediamine,1,4-cyclohexanediamine, or m-xylylenediamine; (2) a ring-openingpolymerization of cyclic lactam, such as ε-caprolactam or Ω-laurolactam;(3) polycondensation of an aminocarboxylic acid, such as 6-aminocaproicacid, 9-aminononanoic acid, 11-aminoundecanoic acid, or12-aminododecanoic acid; or (4) copolymerization of a cyclic lactam witha dicarboxylic acid and a diamine. Specific examples of suitablepolyamides include NYLON 6, NYLON 66, NYLON 610, NYLON 11, NYLON 12,copolymerized NYLON, NYLON MXD6, and NYLON 46.

Formation of the shell and outer core layers of the invention may beaccomplished in a variety of ways, such as those disclosed in U.S. Pat.Nos. 5,480,155; 6,315,683, and 8,262,508, the disclosures of which areincorporated herein, in their entirety, by reference thereto.

In one embodiment, the golf ball of the present invention includes ahollow core. The hollow core is formed from a shell layer that bordersand defines the shape of the innermost aspherical hollow portion. Theshell layer is formed from a thermoset rubber composition and has anouter surface and an inner surface. In this embodiment, a single outercore layer is formed around the shell layer to create a hollow golf ballcore. The outer core layer is also formed from a thermoset material,which may be the same rubber composition as the shell layer but may be adifferent thermoset rubber composition.

A single cover layer or multiple cover layers may be formed over thethermoset/thermoset hollow core. In one single cover layer embodiment,the cover comprises an ionomer having a hardness of at least 55 Shore D.

Alternatively, in another embodiment, a dual cover construction, aninner cover layer and an outer cover layer are formed over the core. Inone embodiment, the inner cover includes an ionomeric material and theouter cover layer includes a polyurea or a polyurethane. The outer coverlayer is typically softer than the inner cover layer, such as where theinner cover has a hardness of greater than about 60 Shore D and theouter cover layer has a hardness of less than about 60 Shore D; however,the reverse may be used.

In the above embodiment, the plurality of extensions and innermostaspherical hollow portion, combined, can have a diameter of about 0.51to 1.1 inches. The surface hardness of the shell layer is preferablygreater than the hardness of the inner surface of the shell layer byabout 3 to 25 Shore C to define a first hardness gradient. In anotherembodiment, the thermoset outer core layer has a hardness gradient thatis different from the hardness gradient of the thermoset shell layer.Most preferably, the shell layer has a surface hardness greater thanabout 55 Shore C.

The thermoset shell layer has a coefficient of restitution (COR) lessthan about 0.750 when measured at an incoming velocity of 125 ft/s.Preferably, the COR is less than about 0.700, more preferably about0.500 to 0.700, and most preferably about 0.600 to 0.700. The overallhollow core (the combination of the thermoset shell layer and thethermoset outer core layer) has a COR, measured at an incoming velocityof 125 ft/s, higher than the COR of the shell layer by greater thanabout 5%, more preferably about 10 to 50%, and most preferably about 15to 30%.

In an alternative embodiment, the hardness gradient of the thermosetouter core layer has a ‘zero hardness gradient’. The zero hardnessgradient is typically about 0 Shore C (defined herein as ±2 Shore C).The hardness gradient of the thermoset outer core layer may also have a‘negative hardness gradient’, preferably about 3 to 25 Shore C, morepreferably about 5 to 20 Shore C, and most preferably about 8 to 15Shore C. The hardness gradient of the thermoset outer core layer mayalso have a ‘positive hardness gradient’, preferably about 3 to 25 ShoreC, more preferably about 5 to 20 Shore C, and most preferably about 8 to15 Shore C.

The golf ball has a first volume and the plurality of extensions andinnermost aspherical hollow portion, combined, has a second volume. Thesecond volume is about 2% to 30% of the first volume, or the secondvolume is about 5% to 25% of the first volume, or the second volume isabout 10% to 20% of the first volume.

In another embodiment of the invention, the hollow core further includesa thermoplastic intermediate core layer disposed between the thermosetshell layer and the thermoset outer core layer. In still anotherembodiment, the hollow core further includes a thermoset intermediatecore layer disposed between the thermoset shell layer and the thermosetouter core layer. The intermediate core layer may formed from athermoset rubber composition which is the same or different from thethermoset rubber compositions used to form the thermoset shell layer orthe thermoset outer core layer. In these embodiments, the plurality ofextensions and innermost aspherical hollow portion, combined, preferablyhas a diameter of about 0.15 to 1.1 inches, the shell layer has asurface hardness greater than an inner surface hardness by about 10 to25 Shore C to define a hardness gradient, preferably a ‘positivehardness gradient’. The thermoset outer core layer preferably has ahardness gradient that is different from the hardness gradient of theshell layer or the intermediate layer.

In another embodiment of the invention, the hollow core further includesa thermoplastic intermediate core layer disposed between thethermoplastic shell layer and the thermoplastic outer core layer. Instill another embodiment, the hollow core further includes a thermosetintermediate core layer disposed between the thermoplastic shell layerand the thermoplastic outer core layer. The intermediate core layer ispreferably formed from a thermoset rubber composition. In theseembodiments, the plurality of extensions and innermost aspherical hollowportion, combined, preferably has a diameter of about 0.15 to 1.1inches, the thermoplastic shell layer has a surface hardness greaterthan an inner surface hardness by about 1 to 10 Shore C to define ahardness gradient, preferably a ‘positive hardness gradient’. Thethermoplastic outer core layer preferably has a hardness gradient thatis different from the hardness gradient of the thermoplastic shell layeror the intermediate layer.

The golf ball of the present invention includes a hollow core which isformed from a shell layer having a plurality of extensions that borderand shape the innermost aspherical hollow portion. The shell layer isformed from a thermoplastic composition, preferably a conventionalionomer or a fully-neutralized ionomer. The shell layer has an outersurface and an inner surface. A single thermoplastic outer core layer isformed over the shell layer and preferably includes an ionomericcomposition. The combination of the thermoplastic shell layer and thethermoplastic outer core layer results in a thermoplastic/thermoplastichollow core. Typically, an inner cover layer and an outer cover layerare formed over the thermoplastic outer core layer. In one embodiment,the inner cover includes an ionomeric material and the outer coverincludes a polyurea or, more preferably, a polyurethane. The outer coveris preferably softer than the inner cover layer.

The plurality of extensions and innermost aspherical hollow portion,combined, has a diameter of about 0.15 to 1.1 inches, preferably about0.25 to 1.0 inches, more preferably about 0.25 to 0.75 inches, and mostpreferably about 0.3 to 0.5 inches. The surface hardness of thethermoplastic shell layer is preferably greater than the hardness of theinner surface of the shell layer by about 0 to 5 Shore C to define ahardness gradient. The thermoplastic outer core layer also has ahardness gradient, which is the same as or greater than the hardnessgradient of the thermoplastic shell layer. In an alternative embodiment,the hardness gradient of the thermoplastic outer core layer has a ‘zerohardness gradient’. The zero hardness gradient is typically about 0Shore C (defined herein as ±2 Shore C). The hardness gradient of thethermoplastic outer core layer may also have a ‘negative hardnessgradient’, preferably about 1 to 10 Shore C, more preferably about 2 to8 Shore C, and most preferably about 3 to 5 Shore C. The hardnessgradient of the thermoplastic outer core layer may also have a ‘positivehardness gradient’, preferably about 1 to 10 Shore C, more preferablyabout 2 to 8 Shore C, and most preferably about 3 to 5 Shore C.

The golf ball has a first volume and the plurality of extensions andinnermost aspherical hollow portion, combined, has a second volume. Thesecond volume is about 2% to 30% of the first volume, more preferablyabout 5% to 25% of the first volume, and most preferably about 10% to20% of the first volume.

The thermoplastic shell layer has a COR less than about 0.750 whenmeasured at an incoming velocity of 125 ft/s. Preferably, the COR isless than about 0.700, more preferably about 0.500 to 0.700, and mostpreferably about 0.600 to 0.700. The overall hollow core (thecombination of the thermoplastic shell layer and the thermoplastic outercore layer has a COR, measured at an incoming velocity of 125 ft/s,higher than the COR of the shell layer by greater than about 5%, morepreferably about 10 to 50%, and most preferably about 15 to 30%.

In another embodiment of the invention, the hollow core further includesa thermoplastic intermediate core layer disposed between thethermoplastic shell layer and the thermoplastic outer core layer. Instill another embodiment, the hollow core further includes a thermosetintermediate core layer disposed between the thermoplastic shell layerand the thermoplastic outer core layer. The intermediate core layer ispreferably formed from a thermoset rubber composition. In theseembodiments, the plurality of extensions and innermost aspherical hollowportion, combined, preferably has a diameter of about 0.15 to 1.1inches, the thermoplastic shell layer has a surface hardness greaterthan an inner surface hardness by about 1 to 10 Shore C to define ahardness gradient, preferably a ‘positive hardness gradient’. Thethermoplastic outer core layer preferably has a hardness gradient thatis different from the hardness gradient of the thermoplastic shell layeror the intermediate layer.

The plurality of extensions and innermost aspherical hollow portion,combined, has a diameter of about 0.15 to 1.1 inches, preferably about0.25 to 1.0 inches, more preferably about 0.25 to 0.75 inches, and mostpreferably about 0.3 to 0.5 inches. The surface hardness of thethermoplastic shell layer is preferably greater than the hardness of theinner surface of the shell layer by about 1 to 5 Shore C to define afirst hardness gradient. The thermoset outer core layer has a secondhardness gradient, which is greater than the hardness gradient of thethermoplastic shell layer. In an alternative embodiment, the hardnessgradient of the thermoset outer core layer has a ‘zero hardnessgradient’. The zero hardness gradient is typically about 0 Shore C(defined herein as ±2 Shore C). The hardness gradient of the thermosetouter core layer may also have a ‘negative hardness gradient’,preferably about 3 to 25 Shore C, more preferably about 5 to 20 Shore C,and most preferably about 8 to 15 Shore C. The hardness gradient of thethermoset outer core layer may also have a ‘positive hardness gradient’,preferably about 3 to 25 Shore C, more preferably about 5 to 20 Shore C,and most preferably about 8 to 15 Shore C.

In another embodiment of the invention, the hollow core further includesa thermoplastic intermediate core layer disposed between the shell layerand the thermoset outer core layer. The thermoplastic intermediate corelayer may be formed from a thermoplastic material that is the same ordifferent from the thermoplastic material of the shell layer. In stillanother embodiment, the hollow core further includes a thermosetintermediate core layer disposed between the thermoplastic shell layerand the thermoset outer core layer. The intermediate core layer mayformed from a thermoset rubber composition which is the same ordifferent from the thermoset rubber composition used to form thethermoset outer core layer. In these embodiments, the plurality ofextensions and innermost aspherical hollow portion, combined, preferablyhas a diameter of about 0.15 to 1.1 inches, the thermoplastic shelllayer has a surface hardness greater than an inner surface hardness byabout 1 to 5 Shore C to define a first hardness gradient, preferably a‘positive hardness gradient’, and the thermoset outer core layer orthermoset intermediate core layer has a second hardness gradient.

In another embodiment, the inventive golf ball includes the hollow core.The hollow core includes a shell layer formed from a first thermosetrubber composition. The shell layer has an outer surface, an innersurface, and extensions located on the inner surface that define andshape the innermost aspherical hollow portion. In this embodiment, asingle thermoplastic outer core layer is disposed about the shell layerto complete the hollow core. A single cover or, preferably, an innercover layer is formed around the outer core layer. When an inner coverlayer is present, an outer cover layer is formed over the inner coverlayer. Most preferably, the inner cover is formed from an ionomericmaterial and the outer cover layer is formed from a polyurethanematerial, and the outer cover layer has a hardness that is less thanthat of the inner cover layer. Preferably, the inner cover has ahardness of greater than about 60 Shore D and the outer cover layer hasa hardness of less than about 60 Shore D.

The plurality of extensions and innermost aspherical hollow portion,combined, has a diameter of about 0.15 to 1.1 inches, preferably about0.25 to 1.0 inches, more preferably about 0.25 to 0.75 inches, and mostpreferably about 0.3 to 0.5 inches. In this embodiment, the shell layerhas a surface hardness that is greater than its inner surface hardnessby about 3 to 25 Shore C to define a first hardness gradient.

The thermoplastic outer core layer has a second hardness gradient. Theshell layer has a surface hardness greater than about 55 Shore C. Theshell layer has a coefficient of restitution (COR) less than about 0.750when measured at an incoming velocity of 125 ft/s. Preferably, the CORis less than about 0.700, more preferably about 0.500 to 0.700, and mostpreferably about 0.600 to 0.700. The overall core (the combination ofthe hollow core and any outer core layers) has a COR, measured at anincoming velocity of 125 ft/s, higher than the COR of the shell layer bygreater than about 5%, more preferably about 10 to 50%, and mostpreferably about 15 to 30%.

In an alternative embodiment, the hardness gradient of the thermoplasticouter core layer has a ‘zero hardness gradient’. The zero hardnessgradient is typically about 0 Shore C (defined herein as ±2 Shore C).The hardness gradient of the thermoplastic outer core layer may alsohave a ‘negative hardness gradient’, preferably about 1 to 10 Shore C,more preferably about 2 to 8 Shore C, and most preferably about 2 to 5Shore C. The hardness gradient of the thermoplastic outer core layer mayalso have a ‘positive hardness gradient’, preferably about 1 to 10 ShoreC, more preferably about 2 to 8 Shore C, and most preferably about 2 to5 Shore C.

The golf ball has a first volume and the plurality of extensions andinnermost aspherical hollow portion, combined, has a second volume. Thesecond volume is about 2% to 30% of the first volume, more preferablyabout 5% to 25% of the first volume, and most preferably about 10% to20% of the golf ball volume.

The hollow core of the present invention (innermost aspherical hollowportion, shell layer and outer core layer(s)) is covered by at least onecover layer. An intermediate layer, such as an inner cover layer, mayoptionally be disposed about the hollow core, with the cover layerformed around the intermediate layer as an outer cover layer. While anyof the thermoplastic materials disclosed herein may be suitable for theinner or outer cover layers of the invention, in one embodiment theoutermost cover is formed from a castable polyurea or a castablepolyurethane; castable hybrid poly(urethane/urea); and castable hybridpoly(urea/urethane). Suitable polyurethanes include those disclosed inU.S. Pat. Nos. 5,334,673 and 6,506,851. Suitable polyureas include thosedisclosed in U.S. Pat. Nos. 5,484,870 and 6,835,794. These patents areincorporated herein by reference thereto.

Other suitable polyurethane compositions comprise a reaction product ofat least one polyisocyanate and at least one curing agent. The curingagent can include, for example, one or more polyamines, one or morepolyols, or a combination thereof. The polyisocyanate can be combinedwith one or more polyols to form a prepolymer, which is then combinedwith the at least one curing agent. Thus, the polyols described hereinare suitable for use in one or both components of the polyurethanematerial, i.e., as part of a prepolymer and in the curing agent. Moresuitable polyurethanes are described in U.S. Pat. No. 7,331,878, whichis incorporated by reference in its entirety.

Any polyisocyanate available to one of ordinary skill in the art issuitable for use according to the invention. Exemplary polyisocyanatesinclude, but are not limited to, 4,4′-diphenylmethane diisocyanate(MDI); polymeric MDI; carbodiimide-modified liquid MDI;4,4′-dicyclohexylmethane diisocyanate (H₁₂MDI); p-phenylene diisocyanate(PPDI); m-phenylene diisocyanate (MPDI); toluene diisocyanate (TDI);3,3′-dimethyl-4,4′-biphenylene diisocyanate; isophoronediisocyanate;1,6-hexamethylene diisocyanate (HDI); naphthalene diisocyanate; xylenediisocyanate; p-tetramethylxylene diisocyanate; m-tetramethylxylenediisocyanate; ethylene diisocyanate; propylene-1,2-diisocyanate;tetramethylene-1,4-diisocyanate; cyclohexyl diisocyanate;dodecane-1,12-diisocyanate; cyclobutane-1,3-diisocyanate;cyclohexane-1,3-diisocyanate; cyclohexane-1,4-diisocyanate;1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane; methylcyclohexylene diisocyanate; triisocyanate of HDI; triisocyanate of2,4,4-trimethyl-1,6-hexane diisocyanate; tetracene diisocyanate;napthalene diisocyanate; anthracene diisocyanate; isocyanurate oftoluene diisocyanate; uretdione of hexamethylene diisocyanate; andmixtures thereof. Polyisocyanates are known to those of ordinary skillin the art as having more than one isocyanate group, e.g.,di-isocyanate, triisocyanate, and tetra-isocyanate. Preferably, thepolyisocyanate includes MDI, PPDI, TDI, or a mixture thereof, and morepreferably, the polyisocyanate includes MDI. It should be understoodthat, as used herein, the term MDI includes 4,4′-diphenylmethanediisocyanate, polymeric MDI, carbodiimide-modified liquid MDI, andmixtures thereof and, additionally, that the diisocyanate employed maybe “low free monomer,” understood by one of ordinary skill in the art tohave lower levels of “free” monomer isocyanate groups, typically lessthan about 0.1% free monomer isocyanate groups. Examples of “low freemonomer” diisocyanates include, but are not limited to Low Free MonomerMDI, Low Free Monomer TDI, and Low Free Monomer PPDI. The at least onepolyisocyanate should have less than about 14% unreacted NCO groups.Preferably, the at least one polyisocyanate has no greater than about8.0% NCO, more preferably no greater than about 7.8%, and mostpreferably no greater than about 7.5% NCO with a level of NCO of about7.2 or 7.0, or 6.5% NCO commonly used.

Any polyol available to one of ordinary skill in the art is suitable foruse according to the invention. Exemplary polyols include, but are notlimited to, polyether polyols, hydroxy-terminated polybutadiene(including partially/fully hydrogenated derivatives), polyester polyols,polycaprolactone polyols, and polycarbonate polyols. In one embodiment,the polyol includes polyether polyol. Examples include, but are notlimited to, polytetramethylene ether glycol (PTMEG), polyethylenepropylene glycol, polyoxypropylene glycol, and mixtures thereof. Thehydrocarbon chain can have saturated or unsaturated bonds andsubstituted or unsubstituted aromatic and cyclic groups. Preferably, thepolyol of the present invention includes PTMEG.

In another embodiment, polyester polyols are included in thepolyurethane material. Suitable polyester polyols include, but are notlimited to, polyethylene adipate glycol; polybutylene adipate glycol;polyethylene propylene adipate glycol; o-phthalate-1,6-hexanediol;poly(hexamethylene adipate) glycol; and mixtures thereof. Thehydrocarbon chain can have saturated or unsaturated bonds, orsubstituted or unsubstituted aromatic and cyclic groups.

In another embodiment, polycaprolactone polyols are included in thematerials of the invention. Suitable polycaprolactone polyols include,but are not limited to, 1,6-hexanediol-initiated polycaprolactone,diethylene glycol initiated polycaprolactone, trimethylol propaneinitiated polycaprolactone, neopentyl glycol initiated polycaprolactone,1,4-butanediol-initiated polycaprolactone, and mixtures thereof. Thehydrocarbon chain can have saturated or unsaturated bonds, orsubstituted or unsubstituted aromatic and cyclic groups.

In yet another embodiment, polycarbonate polyols are included in thepolyurethane material of the invention. Suitable polycarbonates include,but are not limited to, polyphthalate carbonate and poly(hexamethylenecarbonate) glycol. The hydrocarbon chain can have saturated orunsaturated bonds, or substituted or unsubstituted aromatic and cyclicgroups. In one embodiment, the molecular weight of the polyol is fromabout 200 to about 4000.

Polyamine curatives are also suitable for use in the polyurethanecomposition of the invention and have been found to improve cut, shear,and impact resistance of the resultant balls. Preferred polyaminecuratives include, but are not limited to,3,5-dimethylthio-2,4-toluenediamine and isomers thereof;3,5-diethyltoluene-2,4-diamine and isomers thereof, such as3,5-diethyltoluene-2,6-diamine;4,4′-bis-(sec-butylamino)-diphenylmethane;1,4-bis-(sec-butylamino)-benzene, 4,4′-methylene-bis-(2-chloroaniline);4,4′-methylene-bis-(3-chloro-2,6-diethylaniline);polytetramethyleneoxide-di-p-aminobenzoate; N,N′-dialkyldiamino diphenylmethane; p,p′-methylene dianiline; m-phenylenediamine;4,4′-methylene-bis-(2-chloroaniline);4,4′-methylene-bis-(2,6-diethylaniline);4,4′-methylene-bis-(2,3-dichloroaniline);4,4′-diamino-3,3′-diethyl-5,5′-dimethyl diphenylmethane;2,2′,3,3′-tetrachloro diamino diphenylmethane; trimethylene glycoldi-p-aminobenzoate; and mixtures thereof. Preferably, the curing agentof the present invention includes 3,5-dimethylthio-2,4-toluenediamineand isomers thereof, such as ETHACURE® 300, commercially available fromAlbermarle Corporation of Baton Rouge, La. Suitable polyamine curatives,which include both primary and secondary amines, preferably havemolecular weights ranging from about 64 to about 2000.

At least one of a diol, triol, tetraol, or hydroxy-terminated curativesmay be added to the aforementioned polyurethane composition. Suitablediol, triol, and tetraol groups include ethylene glycol; diethyleneglycol; polyethylene glycol; propylene glycol; polypropylene glycol;lower molecular weight polytetramethylene ether glycol;1,3-bis(2-hydroxyethoxy) benzene;1,3-bis-[2-(2-hydroxyethoxy)ethoxy]benzene;1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}benzene; 1,4-butanediol;1,5-pentanediol; 1,6-hexanediol; resorcinol-di-(β-hydroxyethyl) ether;hydroquinone-di-(β-hydroxyethyl) ether; and mixtures thereof. Preferredhydroxy-terminated curatives include 1,3-bis(2-hydroxyethoxy) benzene;1,3-bis-[2-(2-hydroxyethoxy)ethoxy]benzene;1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}benzene; 1,4-butanediol,and mixtures thereof. Preferably, the hydroxy-terminated curatives havemolecular weights ranging from about 48 to 2000. It should be understoodthat molecular weight, as used herein, is the absolute weight averagemolecular weight and would be understood as such by one of ordinaryskill in the art.

Both the hydroxy-terminated and amine curatives can include one or moresaturated, unsaturated, aromatic, and cyclic groups. Additionally, thehydroxy-terminated and amine curatives can include one or more halogengroups. The polyurethane composition can be formed with a blend ormixture of curing agents. If desired, however, the polyurethanecomposition may be formed with a single curing agent.

In one embodiment of the present invention, saturated polyurethanes areused to form one or more of the cover layers, preferably the outer coverlayer, and may be selected from both castable thermoset andthermoplastic polyurethanes. In this embodiment, the saturatedpolyurethanes of the present invention are substantially free ofaromatic groups or moieties. Saturated polyurethanes suitable for use inthe invention are a product of a reaction between at least onepolyurethane prepolymer and at least one saturated curing agent. Thepolyurethane prepolymer is a product formed by a reaction between atleast one saturated polyol and at least one saturated diisocyanate. Asis well known in the art, that a catalyst may be employed to promote thereaction between the curing agent and the isocyanate and polyol, or thecuring agent and the prepolymer.

Additionally, polyurethane can be replaced with or blended with apolyurea material. Polyureas are distinctly different from polyurethanecompositions. The polyurea-based compositions are preferably saturatedin nature. The polyurea compositions may be formed from the reactionproduct of an isocyanate and polyamine prepolymer crosslinked with acuring agent. For example, polyurea-based compositions of the inventionmay be prepared from at least one isocyanate, at least one polyetheramine, and at least one diol curing agent or at least one diamine curingagent.

Golf balls of the invention and any thermoplastic or thermoset layerdisclosed herein may be formed using a variety of application techniquessuch as compression molding, flip molding, injection molding,retractable pin injection molding, reaction injection molding (RIM),liquid injection molding (LIM), casting, vacuum forming, powder coating,flow coating, spin coating, dipping, spraying, and the like.Conventionally, compression molding and injection molding are applied tothermoplastic materials, whereas RIM, liquid injection molding, andcasting are employed on thermoset materials. These and other manufacturemethods are disclosed in U.S. Pat. Nos. 6,207,784 and 5,484,870, thedisclosures of which are incorporated herein by reference in theirentirety.

For example, intermediate or cover layers may be formed using anysuitable method known to those of ordinary skill in the art such as byblow molding an intermediate layer and covering with a dimpled coverlayer formed by injection molding, compression molding, casting, vacuumforming, powder coating, and the like. A composition may be dry-blendedand fed into an injection molding machine to produce half cups, or maybe formed by melt blending and extruding the components with polymermixing equipment, such as a single or twin-screw extruder. Pellets maybe dry blended with other components and then injection molded onto anyinner layer. Compression molding or retractable pin injection moldingmay be used to seal cups together and form a finished golf ball.

A method of injection molding using a split vent pin can be found inco-pending U.S. Pat. No. 6,877,974, filed Dec. 22, 2000, entitled “SplitVent Pin for Injection Molding.” Examples of retractable pin injectionmolding may be found in U.S. Pat. Nos. 6,129,881; 6,235,230; and6,379,138. These molding references are incorporated in their entiretyby reference herein. In addition, a chilled chamber, i.e., a coolingjacket, such as the one disclosed in U.S. Pat. No. 6,936,205, filed Nov.22, 2000, entitled “Method of Making Golf Balls” may be used to cool thecompositions of the invention when casting, which also allows for ahigher loading of catalyst into the system.

Conventionally, compression molding and injection molding are applied tothermoplastic materials, whereas RIM, liquid injection molding, andcasting are employed on thermoset materials. These and other manufacturemethods are disclosed in U.S. Pat. Nos. 6,207,784 and 5,484,870, thedisclosures of which are incorporated herein by reference in theirentirety.

Castable reactive liquid polyurethanes and polyurea materials may beapplied over the inner ball using a variety of application techniquessuch as casting, injection molding spraying, compression molding,dipping, spin coating, or flow coating methods that are well known inthe art. In one embodiment, the castable reactive polyurethanes andpolyurea material is formed over the core using a combination of castingand compression molding. Conventionally, compression molding andinjection molding are applied to thermoplastic cover materials, whereasRIM, liquid injection molding, and casting are employed on thermosetcover materials.

U.S. Pat. No. 5,733,428, the entire disclosure of which is herebyincorporated by reference, discloses a method for forming a polyurethanecover on a golf ball core. Because this method relates to the use ofboth casting thermosetting and thermoplastic material as the golf ballcover, wherein the cover is formed around the core by mixing andintroducing the material in mold halves, the polyurea compositions mayalso be used employing the same casting process.

For example, once a polyurea composition is mixed, an exothermicreaction commences and continues until the material is solidified aroundthe core. It is important that the viscosity be measured over time, sothat the subsequent steps of filling each mold half, introducing thecore into one half and closing the mold can be properly timed foraccomplishing centering of the core cover halves fusion and achievingoverall uniformity. A suitable viscosity range of the curing urea mixfor introducing cores into the mold halves is determined to beapproximately between about 2,000 cP and about 30,000 cP, or within arange of about 8,000 cP to about 15,000 cP.

To start the cover formation, mixing of the prepolymer and curative isaccomplished in a motorized mixer inside a mixing head by feedingthrough lines metered amounts of curative and prepolymer. Top preheatedmold halves are filled and placed in fixture units using centering pinsmoving into apertures in each mold. At a later time, the cavity of abottom mold half, or the cavities of a series of bottom mold halves, isfilled with similar mixture amounts as used for the top mold halves.After the reacting materials have resided in top mold halves for about40 to about 100 seconds, preferably for about 70 to about 80 seconds, acore is lowered at a controlled speed into the gelling reacting mixture.

A ball cup holds the shell through reduced pressure (or partial vacuum).Upon location of the core in the halves of the mold after gelling forabout 4 to about 12 seconds, the vacuum is released allowing the core tobe released. In one embodiment, the vacuum is released allowing the coreto be released after about 5 seconds to 10 seconds. The mold halves,with core and solidified cover half thereon, are removed from thecentering fixture unit, inverted and mated with second mold halveswhich, at an appropriate time earlier, have had a selected quantity ofreacting polyurea prepolymer and curing agent introduced therein tocommence gelling.

Similarly, U.S. Pat. No. 5,006,297 and U.S. Pat. No. 5,334,673 both alsodisclose suitable molding techniques that may be utilized to apply thecastable reactive liquids employed in the present invention.

However, golf balls of the invention may be made by any known techniqueto those skilled in the art.

While any of the embodiments herein may have any known dimple number andpattern, a the number of dimples may be 252 to 456, or 330 to 392, forexample. The dimples may comprise any width, depth, and edge angledisclosed in the prior art and the patterns may comprises multitudes ofdimples having different widths, depths and edge angles. The partingline configuration of said pattern may be either a straight line or astaggered wave parting line (SWPL). Most preferably the dimple number is330, 332, or 392 and comprises 5 to 7 dimples sizes and the parting lineis a SWPL.

In any of these embodiments the single-layer core may be replaced with a2 or more layer core wherein at least one core layer has a negativehardness gradient. Other than in the operating examples, or unlessotherwise expressly specified, all of the numerical ranges, amounts,values and percentages such as those for amounts of materials and othersin the specification may be read as if prefaced by the word “about” eventhough the term “about” may not expressly appear with the value, amountor range. Accordingly, unless indicated to the contrary, the numericalparameters set forth in the specification and attached claims areapproximations that may vary depending upon the desired propertiessought to be obtained by the present invention. At the very least, andnot as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Furthermore, when numerical ranges ofvarying scope are set forth herein, it is contemplated that anycombination of these values inclusive of the recited values may be used.

While it is apparent that the illustrative embodiments of the inventiondisclosed herein fulfill the objective stated above, it is appreciatedthat numerous modifications and other embodiments may be devised bythose skilled in the art. Therefore, it will be understood that theappended claims are intended to cover all such modifications andembodiments, which would come within the spirit and scope of the presentinvention.

What is claimed is:
 1. A golf ball comprising: a hollow core comprising:an innermost spherical hollow portion having a diameter of about 0.15inches to about 1.1 inches; surrounded by a shell layer formed from athermoplastic composition; and at least one outer core layer formed froma thermoset composition; wherein the shell layer is at least partiallynon-continuous, having a plurality of hollow spaces therein that extendfrom an inner surface to an outer surface of the shell layer and aresymmetrically spaced within the shell layer; and wherein the innersurface has an inner surface hardness and the outer surface has an outersurface hardness greater than the inner surface hardness by up to about7 Shore C to define a first hardness gradient; and wherein the outercore layer has a second hardness gradient and is formed about the outersurface and within the plurality of hollow spaces; and at least onecover layer disposed about the core.
 2. The golf ball of claim 1,wherein the outer core layer has a second inner surface having a secondinner surface hardness that differs from the inner surface hardness. 3.The golf ball of claim 1, wherein the first hardness gradient is about 1to 5 Shore C.
 4. The golf ball of claim 1, wherein the shell layer isperforated.
 5. The golf ball of claim 1, wherein the shell layer is ascreen or a lattice.
 6. The golf ball of claim 1, wherein the secondhardness gradient is a negative hardness gradient of about 3 to 25 ShoreC.
 7. The golf ball of claim 1, wherein the second hardness gradient isa positive hardness gradient of about 3 to 25 Shore C.
 8. The golf ballof claim 1, wherein the cover comprises an inner cover layer disposedabout the outer core layer and comprising an ionomeric material andhaving a first hardness; and an outer cover layer disposed about theinner cover layer and comprising a polyurea or a polyurethane and havinga second hardness less than the first.
 9. A golf ball comprising: a corecomprising: an innermost aspherical hollow portion having a volumeV_(ahp); surrounded by a shell layer that is formed from a thermoplasticcomposition and has an inner surface comprising a plurality ofsymmetrically spaced extensions that border and define a shape of theinnermost aspherical hollow portion; wherein the plurality of extensionsand innermost aspherical hollow portion, combined, form a phantom spherehaving a diameter of from about 0.15 inches to about 1.1 inches; andwherein the plurality of extensions have a combined total volume E_(TV)such that V_(ahp)≧E_(TV)>0.20 (E_(TV)+V_(ahp)); and wherein the shelllayer is at least partially non-continuous, having a plurality of hollowspaces therein that extend from the inner surface to an outer surface ofthe shell layer and are symmetrically spaced within the shell layer; andat least one outer core layer that is formed about the outer surface;wherein the inner surface has an inner surface hardness and the outersurface has an outer surface hardness greater than the inner surfacehardness by up to about 7 Shore C to define a first hardness gradient;and wherein the outer core layer has a second hardness gradient; and atleast one cover layer disposed about the outer core layer.
 10. The golfball of claim 9, wherein the aspherical hollow portion has a shape thatis axially symmetric.
 11. The golf ball of claim 10, wherein theaspherical hollow portion is at least one of non-spherical orirregularly-shaped.
 12. The golf ball of claim 9, wherein the pluralityof extensions and innermost aspherical hollow portion, combined, form aspherical phantom sphere having a diameter of from about 0.30 inches toabout 0.90 inches.
 13. The golf ball of claim 9, wherein the outer corelayer has a second inner surface having a second inner surface hardnessthat differs from the inner surface hardness.
 14. The golf ball of claim9, wherein the first hardness gradient is about 1 to 5 Shore C.
 15. Thegolf ball of claim 9, wherein the shell layer is a screen or a lattice.16. The golf ball of claim 9, wherein the at least one cover layercomprises an inner cover layer disposed about the outer core layer, andan outer cover layer disposed about the inner cover layer, wherein theinner cover layer comprises an ionomeric material and has a firsthardness and the outer cover layer comprises a polyurea or apolyurethane and has a second hardness less than the first.
 17. The golfball of claim 9, wherein the innermost aspherical hollow portion, shelllayer and outer core layer, combined, have an outer diameter of fromabout 0.75 inches to about 1.62 inches.
 18. The golf ball of claim 9,wherein the second hardness gradient is a negative hardness gradient ofabout 3 to 25 Shore C.
 19. The golf ball of claim 9, wherein the secondhardness gradient is a positive hardness gradient of about 3 to 25 ShoreC.
 20. The golf ball of claim 9, wherein the outer core layer is formedfrom a thermoset composition.
 21. The golf ball of claim 9, wherein atleast one outer core layer is formed from a thermoplastic composition.22. A golf ball comprising: a core comprising: a shell layer that isformed from a thermoplastic composition and has an inner surfacecomprising a plurality of symmetrically spaced extensions that borderand define a shape of an innermost aspherical hollow portion; whereinthe innermost aspherical hollow portion comprise from about 2% to about30% of a total volume of the golf ball; and wherein the shell layer isat least partially non-continuous, having a plurality of hollow spacestherein that extend from the inner surface to an outer surface of theshell layer and are symmetrically spaced within in the shell layer; andat least one outer core layer that is formed about the outer surface;wherein the inner surface has an inner surface hardness and the outersurface has an outer surface hardness greater than the inner surfacehardness by up to about 7 Shore C to define a first hardness gradient;and wherein the outer core layer has a second hardness gradient; and atleast one cover layer disposed about the core.
 23. The golf ball ofclaim 22, wherein the innermost aspherical hollow portion has a shapethat is axially symmetric.
 24. The golf ball of claim 23, wherein theinnermost aspherical hollow portion is at least one of non-spherical orirregularly-shaped.
 25. The golf ball of claim 22, wherein the pluralityof extensions and innermost aspherical hollow portion, combined, form aphantom sphere having a diameter of from about 0.15 inches to about 1.1inches.
 26. The golf ball of claim 22, wherein the outer core layer hasa second inner surface having a second inner surface hardness thatdiffers from the inner surface hardness.
 27. The golf ball of claim 22,wherein the first hardness gradient is about 1 to 5 Shore C.
 28. Thegolf ball of claim 22, wherein the shell layer is perforated.
 29. Thegolf ball of claim 22, wherein the shell layer is a screen or a lattice.30. The golf ball of claim 22, wherein the at least one cover layercomprises an inner cover layer disposed about the outer core layer, andan outer cover layer disposed about the inner cover layer, wherein theinner cover layer comprises an ionomeric material and has a firsthardness, and the outer cover layer comprises a polyurea or apolyurethane and has a second hardness less than the first.
 31. The golfball of claim 22, wherein the innermost aspherical hollow portion, shelllayer and outer core layer, combined, have an outer diameter of fromabout 0.75 inches to about 1.62 inches.
 32. The golf ball of claim 22,wherein the second hardness gradient is a negative hardness gradient ofabout 3 to 25 Shore C.
 33. The golf ball of claim 22, wherein the secondhardness gradient is a positive hardness gradient of about 3 to 25 ShoreC.
 34. The golf ball of claim 22, wherein at least one outer core layeris formed from a thermoset composition.
 35. The golf ball of claim 22,wherein at least one outer core layer is formed from a thermoplasticcomposition.